Understanding Chemistry Symbols and Valency

If you are new to my channel, do subscribe it and make sure to hit the bell icon so that you would not miss any of my upcoming videos. Hello dear students, welcome to the first part of language of chemistry. This is a very top requested video. For a long time, kids were requesting for this chapter. So kids, I am also involved in math, math mastery and other chapters are also being made. So it took a little time for that, sorry. And before starting the video, let me tell you something about math mastery. Recently kids, what can I say recently? Yes, you can say recently. It must have been a month or even less than a month, we have launched Maths Mastery for you all, for Class 8 students. In Maths Mastery, every chapter of Maths is being explained very well. I have bought the course for the children, it is an affordable course, the children who have bought the course and who are watching now, they know that every chapter is being explained very well. I had also asked the children for contents. So our contents are exactly the same. Like many kids have sent me their contents and I am making videos according to that. And as the kids are getting requests, that first make this chapter, first make that. So according to that, they are getting the video. If you still don't know anything about Maths Mastery, then the link of that is given in the description box. If you also want that your Maths becomes strong, basic Maths is clear, concept is clear, doubts are clear, So you must take Maths Mastery, you must watch the video and if you like it, you must purchase the course. Now without wasting any time, let's get started with the video. Okay, so Language of Chemistry. See, you have read this chapter of Language of Chemistry in class 7. So a lot is related, kids. For example, if you are reading about symbols, you will read about the same as the name of the word. Because you have already read about the symbols. Then you will read the same chapter in class 9, where you will read about the symbols in detail. You have read in class 7, 8 and 9 also, but you will read in more detail. So I am trying here. I will explain you as much as I can in important notes Because I have given a very limited book You will also see notes, I will tell you a lot of things You just keep a copy pen while noting down The important points you will find You will note down the important points and keep going It is going to be very useful, children It is going to be very useful So without wasting time, let's quickly read what is given in this chapter. First of all, see the symbol. What is a symbol? You all know. What is a symbol? If we talk about the symbol of elements, then what are the symbols of elements? The symbols of elements are their letters. Their letters. How do letters mean? One or two letter abbreviation of the name of an element. Like the name of an element. Whatever the name is. Suppose I am talking about hydrogen. So hydrogen has either one letter. or there will be another element which has either one or two letters we write abbreviation in short form we short the name of the element short the name of the element we give a letter or two letter one that becomes their symbol so you have already read the rules of symbol in class 7 we are not going to read about it at all ok, one minute so symbol you see one or two letter abbreviation of the name of an element or short hand abbreviation of the name of the element we call it the definition of symbol now if I talk about hydrogen then what is the symbol of hydrogen? H we have taken first letter of hydrogen and that too in capital for carbon we have taken first letter C and that too in capital mentioned in capital similarly calcium, c-a-l-c-i-u-m, calcium, what is the symbol of calcium? first and second, first two letters, first is in capital and second is in small, for boron it is b, so you know what are the different symbols, you have to do atomic number 1 to 20, you know atomic number, Atomic number from 1 to 20 starts with hydrogen and ends with calcium. What ends with calcium? It has gone to 118. You have to remember till class 10, till 20. So you have to drink the atomic number properly. Drink the atomic number after mixing it. In that, you have to remember in an orderly fashion that after hydrogen, helium comes. Helium comes after Lithium Then their symbols are also important If you don't pay attention to all these things, then there will be a lot of problems So their symbols are also important Like Ca is for Calcium H is for Hydrogen Ba is for Boron If your teacher asks you about any symbol, then you can tell them quickly Be for Beryllium C for Carbon N for Nitrogen So you should remember all these symbols too Ok So you know about the symbols, you have to remember all these Now the new topic for you all, maybe someone has already read about it, but I am sure many children do not know. This is a new topic, Valency and Valence Electrons. It is very simple and very important. Listen carefully to understand it. It is very simple. If you understand it once, then there will be no problem. Ok, so Valency and Valence Electrons. First of all, we will read about Valence Electrons. Then we will go to Valency. Ok, so what are Valence Electrons? What are the valence electrons? See children, as you all know that one atom has many shells are there or not? like here in front you can see oxygen I will show you by making it if I make it in front of you then you will understand more I feel like this see, as we are talking about oxygen so I know the atomic number of oxygen 8 is there ok, you know 8 is there now write its electronic configuration This is called electronic configuration So how much oxygen is there? First goes 2 which you have already read Then 2 out of 8 goes and 6 is left So in the second you fill all 6 electrons This is done So what is its valence shell? Valence shell means last shell So in oxygen, the last shell is K So what is mana? I will call this shell as last shell or valence shell Now you guys skip the word last shell Remember all these words valence shell So valence shell we call the last shell Last shell in which the electron has gone If I see its atomic structure, atomic model So this is our nucleus This has become the first shell How many electrons in the first shell? 2 electrons Then we made the second shell How many are there in the second? 1,2,3,4,5,6 So here this is valence shell, it is L only. It is L only, its name is L. We got to know about valence shell. Now the electrons in valence shell, the electrons in valence shell, we call them valence electrons. Valence shell means the electrons found in the last shell, we will call them valence electrons. Did you understand? What will we call them? Valence electrons. so how many valence electrons are there in oxygen? see how many valence electrons are there in the last shell? 6 there are 6 electrons in the last shell so how many valence electrons are there in oxygen? 6 valence electrons did you understand? if you understood then that's it by the way if I talk about magnesium if I write the electronic configuration of magnesium then it will be 282 if you don't know how this thing happened I have made a video of atomic structure of the first chapter of this you must watch it, it is very important I have already told you about it that means this is not the first time for you this topic is not the first time for you I have already taught you but if you don't know how to decorate electrons then you won't understand this first clear it then watch this so magnesium has K L M electronic configuration 282 I can make it like this so here is the last shell we also call it outer most shell Last shell is also called valence shell and outermost shell. Both are the same name. Don't get confused. How many electrons are there in the last shell? There are two. You can see it here. You can see it from here. There are two. So in this case, how many valence electrons are there? There are two. In the exam, the question comes. Tell me, how will it come? Will it say? It will say like this. How many? If you want, then note down quickly. How many valence electrons are there in nitrogen? Like this. How many valence electrons? are there in nitrogen it gives such a question it will definitely give or the number of valence electron in nitrogen is dash it will give like this so it is very important for you to remember the atomic number see how everything is related so in nitrogen it is 7 Atomic number KL First is 2, second is 5 First is 2 electrons, second is 5 electrons It will come like this So how many electrons are there in the last? 5 So how many valence electrons are there? Answer is 5 So the concept of valence electron is clear According to me there should be no doubt Now it is valency You must have read the definition of valency separately. This is combining the capacity of an element. The capacity to combine an element with another element. The capacity to make a bond. The capacity to combine. This is called valency. But this is the definition. This is its actual definition. This is what we understand. This is a big deal. But this is what you will understand. Now see what is valency. Okay. So. It is the number of electrons an atom can donate or accept to form a chemical bond with another atom. I will explain this with the help of an example. Here, suppose there is an element. Leave the novel gases and I am talking about the other elements. Now, the element will have an atom in it. And you must be knowing that an atom makes a bond with another atom. Do you know one thing? Many elements make a bond with each other That is why many compounds are possible If I talk about water, H2O Hydrogen atom and Oxygen atom Hydrogen is one element, Oxygen is another Both of the atoms have made a bond That is why this compound is made Similarly, the salt you eat, NaCl NaCl, Sodium Chloride Sodium, Na is an element Chlorine is another element If we make a bond of both atoms, then a compound is possible. So remember that different atoms or different elements always try to combine with each other to make a number of compounds. Only then compounds are possible, otherwise compounds are not possible. Otherwise compounds are not possible. Remember that. So when these atoms or elements come together and combine with each other, when they form a bond, So, there are electrons involved. That means, electrons participate in the production of bonds. When a bond is made, the main work of electrons is done. Remember this. So, when a chemical bond is made with one atom and another atom, how many electrons are involved at that time? What happens is, one atom either donates or accepts the other. That means, out of two bonds, Basically, one atom will give its electron and the other will accept the same electron. Meaning, one will donate, lose and the other will accept it and gain it. So, how many electrons are losing or accepting? That is valency. So valency means it is the number of electrons an atom can donate or accept to form a chemical bond with another atom. When one atom forms a chemical bond with another atom, then the number of electrons it is gaining or donating becomes its valency. If you understand it from the example, then you will understand it better. For example, Sodium. Now you don't know whether sodium gains or gives electrons. You don't know this, I will tell you what it does. But for once pay attention that sodium looses one electron, donates one electron to the other. It can't take one electron. Sodium gives one electron. So its valency becomes 1. If I talk about magnesium, do you know how many electrons it has? When it makes a bond with someone, it looses two electrons, it gives them to someone, it donates them. So if you give two electrons here, then its balance becomes two. Did you understand? Similarly, if I talk about oxygen, do you know what oxygen does? It gains electrons, accepts them, takes them. This accepts electrons. Do you know how many electrons it accepts? It accepts two electrons. So when this makes a bond with someone, it takes 2 electrons. It accepts 2 electrons. What is 2 electrons? How many electrons? 2. So its valency is 2. Do you know what nitrogen does to how many electrons? Like nitrogen. Nitrogen also accepts electrons. And do you know how many it takes? It takes 3 electrons. How many? 3. So its valency is 3. Did you understand? So when an atom forms a bond with another, then the amount of electrons it is giving or taking, becomes its valency. That is what becomes its valency. Understood? Now, as we have a very important thing here, which is not given in your book, like not given in Living Science, this is extra, ok? And if it is given in someone's book, then it is very good. Now look kids, now I will tell you this, how will you know which element is given? Will lose electrons and which element? Will gain, will take electrons. How will we know? So remember, the metals, metals always lose electrons, give to the other person. Always. Means the work of metals is that it gives electrons. It always loses electrons, donates, gives. But now the question is, how will you recognize if an element is metal or non-metal? How will you recognise it? It is a very easy way to recognise it. The last cell, the valence cell, has either one electron, two electrons or three electrons. In which? In the last cell. We are not talking about the previous cell, we are talking about the last cell, the outer most cell, the valence cell. So, the metal always has either one, two or three electrons in its last cell. So if you write electronic configuration like this then you will easily recognize it Like I told you about sodium a while ago I told you that sodium's work is to lose electrons So children, I will tell you that will sodium lose or gain Or you tell me what is sodium metal So you will remember the atomic number of sodium and write it Write electronic configuration Now see the last electron How many electrons are there? One. So metal has either one electron outside, or two, or three. In the last shell. So you will recognize that it is metal. And metal always, always loses its valence electron. It will always lose its last electron. It means it will never bond with anyone. So its valence electron, the last electron, it loses it. Remember. So this is how you can find out. So here, you were reading about valency a while ago. That the number of electrons an atom is donating or accepting, we call that valency. So here, sodium will lose one electron. Because there is only one electron in the outer most shell. So the number of electrons in the outer most shell, will donate that number of electrons. Because it is metal, its job is to donate. so the electrons in the outer shell will give to the electrons in the valence shell so it has one electron so it will give one electron to someone and then it will make a bond so much clear and after making a bond and after giving electrons, you know there are changes in them in metals, after giving electrons, after losing them, there are changes a charge comes on them positive charge positive charge comes on metals when? When they give their electrons and then we call them cation. Means when they get positive charge, then we call them cation. What do we call cation? Cation, cation. What do we call cation? Remember cation. Okay. Now as if, now as if. Okay, it is here. It is here. After that I will tell you another example. You must be able to understand, right kids? It is very simple. Now again take sodium. Sodium atomic number 11 is written in electronic configuration 2, 8, 1 So how many electrons are there outside of sodium? 1 electron This is metal You have to first find out whether it is metal or non-metal We have not studied non-metal yet First you have to find out whether it is metal or not So you will write its electronic configuration You see at the end it is 1 that means it is metal And what does metal do? It leaves out the external electrons. How many electrons will it leave out? As many as it has outside. Okay? As many electrons as it has in its last shell, it will leave out the electrons. The people inside do not participate. The electrons inside do not get loose. So sodium has one electron, so what will it do? The last one electron will lose one electron. When it makes a bond with someone, it will lose one electron. So if I make sodium here, KLM, there are three shells, so I made three shells. Two in the first, eight in the second, and one in the last. Okay, this is sodium, Na. After that, if we see how many electrons it will lose, it will lose one electron because it has only one electron outside. So it will lose means this electron will go away from it. So what we will do now, we will see here. The last one has gone, so the first shell is there. In the first shell, there are two electrons. Now this second shell, how many children are there in the second shell? 1, 2, 3, 4, 5, 6, 7, 8. Now I don't have to make the last shell because it has left its electron. so when it leaves the electron, it will create a positive charge on itself so when it releases the electron, it will get a positive charge on itself so you made it that it left one electron, see here there were three shells in the last shell there was one electron but here it is not made in the last shell because it has left one electron so it will get a positive charge So we give a bracket and write plus here. Here I have written only plus, that means plus 1. If I had written plus 2 here, that means it would have left 2 electrons. But does it have 2 electrons outside? No. It left 1 electron, so it is only plus. Plus means plus 1. So this is Na, which means plus charge on sodium. Plus means that it has a lack of an electron. Remember, I have written Na plus here. Na plus means that it has released one of its electrons. Did you understand? It has released one of its electrons. So, see this line too. On losing one electron from the last shell, after losing the last shell or electron, it acquires plus one positive charge. On sodium, plus one. I have not written one here. The meaning is the same. On this, plus one. plus one positive charge will come. So this is very important. Very much. Similarly if I talk about aluminium first of all you have to know that aluminium as I will tell you, ask you will aluminium gain electrons or will it lose? So you first write its electronic configuration. So you know the atomic number you know KLM 283 and write it see that in the last it has 3 electrons 3 are what does it mean it means it is a metal and if it is a metal then it will loose its electrons ok and how many electrons will it loose in the last how many 3 are so 3 electrons will loose understood so it will loose its 3 electrons so first of all I wrote its electronic configuration I saw that it is a metal and it has 3 electrons in the last shell so it will loose all 3 electrons after loosing all 3 electrons there will be a positive charge on the aluminium i.e. plus and I am writing 3 plus because it has loosed all 3 electrons did you understand? did you or not? if I talk about magnesium if I talk about magnesium I will ask you to tell me what is the condition of magnesium It means that there is metal, how will we do it? How will we know? So you will write its electronic configuration 282 So you will see in the last It is 2, that means it is metal It is metal means It will lose the electron, it will give And how many electrons will it lose? How many are there in the last? 2 So it will lose how many? It will lose 2 electrons Understood? It will give 2 electrons Means magnesium After giving 2 electrons 2 plus will be there. Because 2 electrons were lost, positive charge will come. But how much? 2 plus will come. Aluminium was giving 3 electrons, so that became 3 plus. Understood? Now here I have written Al3 plus. Al3 plus means that Aluminium has a 3 electron deficiency. This means that, like I made sodium. Actually, how is sodium? It is like this. 2 8 and 1. This is sodium. 2, 8, 1. K, L, M. Actually, this is what happens. But we know that sodium will lose its external electron. So how will it look? 2. 1, 2, 3, 4, 5, 6, 7, 8 and it will have 8 plus charge that means it will be 2 and 8 just 2 and 8 is K and L so guys, in sodium it actually remains like this ok, in sodium it actually remains 2, 8, 1 but now it has loosed one electron so it became 2 and 8 that means now this Na plus how much electron is missing in it? actually it had one electron extra but Na plus means there is a deficiency of one electron AL3 plus means that Al has a deficiency of three electrons Ca2 plus means that Cal has a deficiency of two electrons did you understand? is it clear? and if I tell you about valency here we were talking about metals earlier ok so metals lose as many electrons as it has outside how many are there outside? either one is or 2 or 3 so outside of it, in the last shell, all the electrons of the metals will be its valency remember, I will teach you further that in metals, in the last shell, all the electrons will be its valency so if I talk about aluminium, I will ask you, tell me how much is the valency of aluminium so you know that it is metal, you write it down you will see that in the last shell, there are 3 electrons so the valency is 3 its valency is 3 in matter it is like this in last shell it will be like this in calcium last shell has 2 electrons so its valency will be 2 there is an exception case exceptional cases if i talk about exceptional cases then hydrogen, hydrogen is different outside of hydrogen it has only one electron and outside of it there is only one you will say that this is not metal yes kids, hydrogen is not metal it is non-metal, this is an exceptional case that outside it there is one electron but it is non-metal ok, helium this is the electronic configuration of helium outside helium there are two electrons but kids this is noble gas not metal, keep writing helium is noble gas, not metal that you will say that helium will loose two electrons, noble gas does not do anything neither accept nor loose and boron boron has two and three boron has three but it is not metal it is a metalloid we will study metalloid later these are exceptional cases you can see that this has one, this has two and this has three the nature of this is matching like a metal because we have studied that metals have one, two or three Here it is the same. But these people are not metal. Are they metal? Not at all. These are exceptional cases. Take a screenshot. Now let's talk about non-metals. Now how will we know if an element is non-metal or not? How will we know? Now how will we know if an element is non-metal or not? So kids remember, outside non-metals, The last shell will have 5, 6 or 7 electrons Where? In the last shell If you take any non-metal name You know that oxygen is a non-metal You must know this You don't know? You know it right? You know that oxygen is a non-metal If I make its electronic configuration It will be 2,6 Nitrogen is also a non-metal I am showing you by making it. Now see these three cases. If any element is non-metal, then its outer most shell, the last shell, should have either 5 electrons or 6 or 7. You will say, why did you leave 4? You took 1, 2 and 3 in metal. You took 5, 6 and 7 in non-metal. Why did you leave 4? Like carbon. K, L, 2 and 4. Children, okay, carbon is also non-metal. But, its case is different. You will study in class 10. I will tell you. I have written somewhere after this, exceptional case. What is there, what is not. So, once you leave the 4 one. When you go to higher classes, take it in 9th. In your concise, I have concise. Where did it go? It is not here. In 9th, you buy concise book for chemistry. Conscience, it is of Selena. Selena publisher. I have noted down the details in the notes on the side. You will read the full actual in the 10th. Not now. So you can see that if there is a non-metal element, then outside that there will be 5, 6 or 7 electrons. What does non-metal do? The nature of non-metal is that it will gain electrons, accept them, take them. What did metal do? It was giving. Non-metal will always gain electrons. Non-metals gain electrons. And after gaining, they get minus charge. What does that do? What was coming on metal? Positive. And what comes on non-metals? Negative. And when they get a negative charge, we call it anions. What do we call it? Anions. What do we call it? Anions. Did you understand? So here you are seeing that these three, oxygen, nitrogen and fluorine, these three are non-metal. So what will these three do? They will gain electrons, they will accept electrons. Their nature is that they accept electrons and after accepting electrons they get minus charge and after getting minus charge we call it anion like after getting positive charge in metal they were called cation now we will call them anions now let us read the example of chlorine ok now What is chlorine? I will tell you about oxygen. Now, let's see about oxygen. Now, children, you have seen that oxygen is non-metal or metal. It is 6 outside, that means it is non-metal. It is non-metal, it is clear. What does non-metal do? It takes or gives electrons. It will gain or accept electrons. Remember, what will non-metal do? It will gain electrons. But the question is, how many electrons will it gain? How many electrons will it gain? How will we know? There is a formula for this. What is the formula? 8 minus valence electrons You have to know how many electrons it will gain So what you have to do is, 8 minus valence electrons How many are there? 6. That means 2 That means it will gain 2 electrons. How many electrons is it taking? 2 electrons. Now After taking 2 electrons, see outside 2 will come, then 8 will come. So, kids, you guys remember one thing. You guys have heard of the name of noble gas, right? Noble gas is absolutely amazing. It lives like a king. Do you know what? Like a king doesn't do any work. It doesn't mean that they will be busy all day. They will be busy all day. They live their life in a comfortable way. Okay? Positive way. They live their life in a comfortable way. Similarly, noble gas, these noble gases have a total of 6 elements. These six elements are very stable. They are not related to anyone. They are lazy and live in comfort. They are not related to anyone. So, apart from the noble gases, all the other elements like oxygen, hydrogen, etc. are irritated by the noble gases. They wish they could become noble gases. They wish they could live like them. They wish they could be stable like them. Do you know why these noble gases are stable? Because the outer most shell of these, if I talk about these, take Argon for example, look at their electronic configuration, 288. Neon, this is also a noble gas. Take this one, 28. So the last shell of this, look, all of them have 8 electrons in the last shell. Where the last shell has 8 electrons, it means it is stable, not just a small one. They will become absolutely stable. So all the other elements think that we wish we had 8 electrons outside. They wish, they all think. And somehow they bring 8 electrons. How do they bring? By making a bond. They make a compound by making a bond with each other. In that case, they also get 8 electrons outside. Means they want to be stable. So all the elements see that which noble gas is near us. I can make the noble gas that I have. Did you understand? And in noble gas, helium is the only exceptional case, outside of which there are two electrons. And this is also stable. It is not that it is not stable. In the case of helium, this is also stable. Outside of it, it has two total electrons. So this is also stable. But the remaining noble gases in the last shell are of 8 electrons. How many? 8 electrons. where 8 comes means Jai Ram ji that means we live very comfortably so all the other elements think that we should also become stable like the noble gases that are near us so this oxygen also wants to be stable so as I was telling you that it will gain because it is non-metal so how much electron will it gain? it wants that the noble gas near it is neon because its atomic number is 8 and its atomic number is 10 so this means that I have 6 electrons in the last cell and I take the electrons so I also make 8 electrons in the last cell so how many electrons will it take to take 8 electrons in the last cell? 2 electrons. That is why I told you the formula 2 electrons are not coming out of the formula so why is it taking 2 electrons? so that it becomes stable so that the last cell becomes stable so how many electrons will it take? 2 electrons If I talk about valency, then how much electron is this oxygen gaining? If you see the definition of valency, then what was there in valency? Number of atom except, means number of electron accepts an atom. So here oxygen is... to stabilize you, how many electrons are you accepting? How many electrons are you taking? 2 electrons are you taking. So the balance of oxygen is 2. Now you understood what the balance of oxygen is? 2 came. Means 2. The balance of oxygen is 2. Understood? And after taking the electrons, look carefully. This will take 2 electrons, oxygen. After taking the electrons, they get a minus charge. What charge? Minus charge. Now look here. As this is oxygen, I made 2 electrons in the first shell and how many are there in the second shell? 1, 2, 3, 4, 5, 6. This is normal oxygen. What will it do? It will gain 2 electrons. It will take 2 electrons. So let's give it 2 electrons. It will take 2 electrons. Here it was KL, here it is 2. And if it takes 2, it was 6, so... and if it takes 2 electrons then it will take 2 electrons in the same shell see kids, it will allow to take 2 electrons in the last shell it is not like it will take 2 electrons in the inner shell it is not like that it will accept 2 electrons in the last shell so in the first shell it was 2 electrons in the second shell it was 6 electrons 1,2,3,4,5,6 and how much it took? it took 2 electrons so it will take 2 electrons in the same shell now see it became stable and after taking 2 electrons, it will get minus charge but how much minus will it get? 2 minus how much? 2 minus because it has accepted 2 electrons so 2 minus charge will come in it understood? sure? and we will call it anion hey kids there is a lot of it if you go inside there is a lot of things here we have talked about chlorine chlorine has 7 valence electrons how? let's see how do we know? if you don't remember the atomic number then you will get stuck you guys remember this thing understood? we also remembered the atomic number but it is easy it happens KLM 287 So the electronic configuration of chlorine is 287 Remember this Remember this, this is something to understand Now Now see if this is metal or non-metal So in the last shell you see 7 So outside non-metals either 5 or 6 or 7 is there So this is non-metal What does non-metal do? Gains electrons So this electron will gain Now Question at a kitna gain karega to formula care eight minus last me jitte be electron hotel to eight minus seven that is one They could they electrons gain karega one electron gain karega Agar ye one electron gain karega its kavalency kita o jayega one o jayega Samajh me aaya to me upper chlorine banati you pala shell me head to up long at chaser pencil seven Anna Dusra me hey eight or lash me kitna seven so one two three four 5, 6, 7. This is done. Now what is chlorine doing? It is accepting 1 electron. We have read it. So when it will accept 1 electron, where will it do it? It will do it in the last shell. It will do it in the last shell. It will do it in the last shell. It will do it in the last shell. So in the second, 2. Sorry, in the second, 8. In the last, how much was it? 7 was there. It was like this. But if it will accept 1 more, then 1 more will come. That means 8. If it accepts 1 electron, then it will get charged. one electron is accepted, so minus one here minus, this will be Cl minus this was chlorine but this is Cl minus you understood, this is chlorine and this is Cl minus so it is like this, you can do it easily like this you can do it very easily, I left a space here to make it, let's make it chlorine has a normal electronic configuration of 287 so here 2 electrons are there, here 8 and here 7 but if it is accepting one electron if it accepts one electron then instead of 7 it will be 8 and this will be Cl-so in first we will put 2 In second we will put 8 In third we will put 8 And this will be CL-Put it like this Ok Let's talk about oxygen We have already read all these things Let's talk about oxygen So in oxygen Normally in last See 6 electrons This is non-metal So this will gain electrons Now the question is How many electrons will it gain? So 8-6 is 2 So it will gain 2 electrons and that will be its valency. How much will its valency be? Its oxygen will be 2. Let's add here. First is 2, second is 6. 2, 2. O2 minus, now see it gained 2 electrons. So 1, 2, 1, 2, 3, 4, 5, 6. And it gained 2 electrons. So it became 2 and 8. Now after gaining 2 electrons, it will get charged with 2 minus. Means, after gaining 2 electrons, this is 2 minus. If it would have done 1, then 1 minus. But it will not do 1. It will gain 2 electrons. Now it has to become 8. Isn't it? It had to bring 8 in the last turn. Is this clear? Now see this thing. I have already told you that all the elements, they all want that like their past noble guests, their electronic configuration should also be done. Means in their last shell 8 electrons should come I have already told you about noble gases So you can see here See I have already told you about this thing But I didn't write it there so I will write it here If you want to know the valency of metal So how do you know the valency of metal? Number of electrons in the last shell In the last shell, the number of electrons will be the valency If we talk about sodium then 281 This is metal, sodium definitely. So if someone asks its valency, what will you see? How much is there in the last shell? There is one electron, so valency is 1. Magnesium's electronic configuration is this. How much is its valency? How much is there in the last shell? If there is 2, then valency is 2. If there is 2 in calcium in the last, then valency is 2. So you have to find the valency of metal. Just look at the last shell. The amount of electrons in it will be its valency. Similarly, how will we find the valency of non-metal? 8 minus number of valency electrons. If someone asks for the valency of fluorine, then the electronic configuration of fluorine is KL, that means 2,7. Fluorine has 9 atomic number. So electronic configuration is 2,7. If someone asks for valency, then don't put 7 here. If you put 7, then it will be wrong. This is non-metal. The formula of non-metal is this, to get valency. 8 minus number of valency electron. So 8 minus 7 is equal to 1. Similarly, chlorine's again 8-7 is equal to 1. Nitrogen's 8-5 is equal to 3. So its valency will come out like this. Some exceptional cases here, yes, see this, non-metals. Now we had read that outside non-metals, either 5 or 6 or 7 are there. Carbon is a non-metal, outside that 4 is there, but I did not write that here. Actually, what happens, children? The carbon that is present, it does not gain any electron because it is non-metal. This carbon is non-metal. So, should it actually gain or not? It should. But what does carbon do? If it takes electron from someone, then it has to spend a lot of energy. Meaning, the use of energy there is very dangerous. So, the carbon thinks that I don't want to take electron at all, I will not keep this mess. So, Carbon shares its electrons with everyone. That's why we don't write 4 electrons. Because we will share the rest. There are different cases in higher classes. You have to remember this. That's why I wrote 5, 6 and 7. But in the case of carbon, there is a lot of energy. Energy is used a lot. Energy consumption, energy consumption. What does carbon think about this? that I will not take from anyone, I will share my electron with someone. This was an exceptional case. Now in your book, This topic is given. What is Variable Valency? As you all know about Valency. We have studied Valency a little while ago. How to find out about metals and non-metals. Similarly, it is Variable Valency. Variable means more than one. More than one. Variable Valency means more than one valency. Like a person has one car. Think like this. Everyone has one car's rule. Okay. But there are some people who have more than one car So suppose here there are many elements and metals Which have one valency But there are some metals which have more than one valency That is what we call as Variable Valency Now children to understand Variable Valency You have to see this diagram first and understand Like this is an atom Here I have made 3 shells according to my own Now We know that normally when we extract valency or for valency, who is responsible? Valency electron. We have read that valency electron is responsible for valency. Okay. So, you have read that metals and non-metals, metal loses all the electrons outside. That is its valency. Non-metals take electrons to aid outside. They take electrons. That is their valency. But one thing you have to keep in mind is that anytime, any element, any metal or any non-metal, if it is loosing an electron, then it will loose its last electron. That means the outer valence electron. If any element is taking electron, non-metal, if it is taking electron, accepting it, then it will accept in the last shell. So normally, for valency, these last shell electrons are responsible. Now if I talk about metal, because in your course it is related to metal. Metal will always lose electrons from the outer shell. Because you have read, metal works to lose electrons. What does metal do? It leaves electrons, loses them. So metals always lose their valence electrons. They always lose them. they will loose the last electrons here and that is why we know about their valency but there are some metals like this some metals like this that you know what they do they will loose their last electrons but with that just last one we call it penultimate cell Means they loose electrons from their valence shell along with their penultimate shell. Why do they do this? Because they are not stable. There are many more reasons. You will learn about this in class 11-12. But if teacher asks you that in this case electrons came out from last shell but why they came out from penultimate shell also. Means why they came out from just inner shell also. So you can say that ma'am maybe to get stable or to get stability. to become stable, to become stable, they are releasing electrons from the inner shell when this happens, then only the metals get more than one valency now did you understand? normally all the metals, what they do is, they release electrons from their valence shell means they loose their valence electrons that is how they get their valency but there are some metals which will release from their valence shell Along with that, they also release from their penultimate shell. Because of that, they get to see more than one variable valency. Like copper. Now this is copper. Copper's symbol is Cu. Copper shows two valencies, one 1 and one 2. Copper shows two valencies, one 1 and one 2. Means, see here there is more than one valency. Now, if copper here plus, means, plus 1, I have not written 1, let's write 1. If Cu plus is shown to you, that means it has released 1 electron. Is it or not? You must know this. And if you see Cu 2 plus, that means copper has donated 2 electrons. It has donated. Remember this. If Cu plus is there, that means copper has donated 1 electron and released it. And if Cu 2 plus is there, that means copper has donated 2 electrons. So the name of Cu plus, we call it cuprous. CU2 plus is called cupric. Its name starts with its Latin name. It is called cuprum. Now, one of these two is small valency. So, the suffix after it is OUS. So, cuprus. And this two is big. So, RIC. RIC is used. This was new. I added extra. If it is in someone's book, then it is good. If it is. Iron also shows more than one valency. Iron has two valencies like 2 and 3. Let me tell you one more thing. I didn't tell you. I have written it here. I have written it in Roman number. I will tell you this. Now, as we know that copper has two valencies. That means copper shows more than one valency. Now, if it is written like this, copper and bracket in Roman number is 1. That means this is talking about Cu+. If it is written like this, copper and Roman number is 2. It will be written in Roman number only It will not be written in Hindu Arabic style Which we read 1,2,3,4 If you write it like that, it will be wrong Listen carefully to what I am saying If it is written in copper and in Roman number in bracket 2 is written That means that copper's valency is 2 And these people are metals So by losing the electron They obtain plus charge Okay, so it is 2 plus Similarly, iron Iron also shows two valencies One is 2 Where did it go? Where did I write? Here it is and one is 3 Iron symbol is Fe What is the symbol of Iron? It is Fe Iron symbol is Fe Iron shows two valences, one 2 and one 3 If written by iron and in bracket Roman number has 2 written That means valence is 2 We will write Fe 2 plus If Roman number has 3, then Fe 3 plus like this name is written with Latin name so this is called ferus and this is feric this valency is smaller than 2 and 3 so OUS is in suffix ferus and here this is bigger than 3 that means feric remember this I have made a lot Now let's talk about lead. Lead symbol is Pb. Okay. Lead also shows two valences. One is 2 and one is 4. If 2 is written in Roman number, that means 2+. And 4 is written, then Pb is 4+. Similarly, mercury. Mercury 1, Mercury 2 That means Hg plus Hg 2 plus Mercury symbol is Hg Now it is 3 3 symbol is Sn 3 The symbol of 3 is Sn. This too again shows 2 valences. One is 2 and one is 4. So if Roman number has 2, that means Sn is 2+. And here Sn is 4+. So kids, here we are studying only metals. Because here everywhere plus has come because these are metals. Metals lose their electrons and obtain positive charge. That's why we have put plus with valence. If you see anywhere, there is a number with plus. Like Sn is 2+. That means this 3 is... They have lost 2 electrons. You should know what the meaning of what you see here is. Okay? SN4+. You guys note down this. It will be useful. SN4+. SN4+, means the tin has lost 4 electrons. It gave 4 electrons. I don't know to whom, but it gave. Understood? Do you know what question comes in variable balance? Why do some metals exhibit variable valency? Why do some metals have variable valency? So what is the answer to that? Why does it happen? The reason is because they lose electrons from valence shell as well as penultimate shell. Did you understand? Because these people release their electrons from valence shell as well as penultimate shell. Now, Now kids we will learn about ions. Ions is a very simple thing. What is it? See. You have read, right? Atoms give electrons. Some take electrons. You have read, right? Some atoms, i.e. metals basically, which lose electrons, donate them. And some accept electrons. So when these people do this work, to take and give electrons, then they get a charge. Or you can say, We will call them ions then. Like, look carefully. Atom, look carefully, open your eyes and see. Atom, if it is also losing electrons, I will write the symbol of electron. Atom minus electron means, when atom loses electrons, it becomes ion. Or atom. plus electron means when atom gains electron then also it becomes ion understood? remember this thing when an atom loses electron or when an atom gains electron then what can we call it? then we call it ion then we call it ion then we call it ion ok and everyone knows about ion that ion is a charged particle ion is a charged particle means there will be a charge in the ion. There are two types of charge, positive and negative. Now see, when an atom loses an electron, you have read about metal, right? When metal loses an electron, what happens? It gets a positive charge. That means the ion here, what will be its charge? Positive. And when an atom gains an electron, it will also get a charge. At that time, there will be a negative charge. and we have given it a name we will call it cation means when an atom loses an electron it becomes cation ok and when an atom gains an electron it becomes anion so here it is all the same the definition of ion comes when an atom loses or gains electrons it becomes a charged particle called ion you understood the meaning of ion now as you are aware that sodium is metal it loses an electron so it loses means it also becomes anion It will become a solid ion. So this is an ion. Ion means charged particle. What will become? Charged particle. Now you know that if it loses, then it will get a positive charge. That's why we write it as Na+. And we will call it cation. Similarly, calcium. Calcium loses its two electrons. It is losing and it also becomes an ion. This will also become a charged particle. And how do we write it? Ca2+. So this will become Ca2+. Similarly, chlorine is non-metal. So what is the work of non-metal to gain electrons? So chlorine gains one electron. So here the atom is gaining electrons. After gaining, it will also become a charged particle. It will become an ion. And here it is gaining, so it will become Cl-If one electron is gained, then Cl-Similarly, nitrogen is again non-metal. It will also gain. It will also take the electron, so it will also become a charged particle. And we write it as N3-Means we will write N and 3-Because it accepts three electrons. So now if we look at it, then ions are of two types, cations and anions. Cations are of positive charge and anions are of negative charge. Question comes, what do you mean by cations? So what will you write? When an atom loses electron, It forms a cation. Or cation is a charged particle. And cation is an... Or write it like this. Cation is an ion which is formed when an atom loses electron. When an atom loses electron. You can write it like this. Similarly, what do you mean by anion? How will you define anion? How will you define anion? Anion is a charged particle. Or anion is an ion. Listen carefully. Anion is an... iron which is formed when a when an atom gains electron if you write it like this then it will be done and you should understand it is not like you will write the definition which I have said by writing it in a rata where you will understand you will frame the definition ok so see I have written here how iron is made when metal loses electron So metal loses electrons and becomes cation. Now how do we call this? For example, Na plus. I will call this sodium ion. Because metals have no problem in writing their names. When metals make cation, they have no problem in writing their names. Na plus is called sodium ion. Ca2+, where you will see plus, then understand that these are cation. So how will you write their name? The name of Ca is calcium and iron. Al3+, aluminum name is iron. Similarly, write K+, potassium and iron. If we talk about non-metals, then non-metals gain electrons. After gaining, they become anions. How do we write their name? As you have seen, this is anion, minus one. So behind their name, IDE is written. Meaning, last one, its name is chlorine. But after NE, IDE is written. IDE is written, basically. Okay? So, chloride ion, oxygen is oxide ion, bromine is bromide ion, N3-is nitride ion. There can be many such examples in your book. You can see them. But we write names like this. Non-metals have an ID and metals have no problem. Write names and add ion. Similarly, children, there are two more categories in iron. One is monoatomic and the other is polyatomic. Monoatomic iron and polyatomic iron. Okay, mono means one. What does mono mean? It means one. Okay, so who is monoatomic? Look carefully. Mono means one. Mono means 1 So if you are looking at an ion like this It can be a cation or anion It can be a plus, a minus or whatever it is Either it will be a plus or a minus So you can see something like this Write the plus and the minus Such an ion which will have only one atom One atom means the atom of one element Like Na+, this is just an atom of sodium Ca2+, this is only calcium N3-, this is only an atom of nitrogen O2-is an oxygen atom, Cl-is an chlorine atom, Al3-is an aluminium atom. So all these ions that you are seeing, there is only one single atom in it. So we will call it a monoatomic ion. So see the definition. An ion that consists of only a single atom with a charge. Meaning a single atom with a charge. So here is 3+, there is a minus, there is a 2-. Such an ion which is made up of a single atom. which is made up of a single atom we call it monoatomic ion there are many examples of monoatomic ion first you see the examples see how many examples are there all have one atom all have hydrogen, sodium, potassium, magnesium, calcium, copper, iron apart from that there is no other in one place, in one bar, there is only one atom only one element atom by the way there are also minus ones how many are there, all are monoatomic All the ions you see, plus and minus, all have single atoms So here we will see cation and anion So first of all hydrogen ion Cation means all will come first So we will give the symbol of hydrogen and put plus It is charged with plus one Sodium ion, Na plus and sodium definitely plus This is charged with plus one You all know that sodium loses one electron that's why it is made of Na+. Similarly potassium loses one electron that's why it is made of K+. The symbol of potassium ion is ions. I am not taking the name of the element. These are not elements but ions. So we can write potassium ion as K+. And its charge is plus 1. Magnesium ion loses 2 electrons. So it is plus 2. Similarly calcium also has look at the iron carefully in copper bracket, roman number has 2 it is like this, it can be like this too and it can be like this too so don't get confused in bracket, here is 2 so it means that it is talking about Cu2+, charge is plus 2 similarly iron has 2 in bracket that means it is talking about Fe2+, and plus 2 in aluminium ion, Al3 plus is there and this is plus 3 so these are the cations, monoatomic ones similarly if I talk about monoatomic anions here is the cation Similarly, if I talk about monoatomic anions, first of all, Hydride ion. Hydride ion means hydrogen. See in the back, IDE, IDE, IDE is written. Hydride means H-. Okay? Valency means, it is charged, minus one. Chloride ion, Cl-. Bromide ion, Br-. Iodide ion, I-. Oxide ion means, it is talking about oxygen, 2-. Sulphide ion means, it is talking about sulfur. So, the symbol of sulfur is S. and its 2-that means it accepts 2 electrons here you are seeing here is phosphide ion, talking about phosphorus P is 3-that means here phosphorus has gained 3 electrons N3-nitrogen has gained 3 electrons sulphide S2-sulphur has gained 2 electrons and here is the charge now you will be confused here what? you will say madam here also hydrogen is there Plus may be hydrogen hey, yeah, but it's the Bachu hydrogen exceptional cases hydrogen. Okay, hi doesn't know plus be when I tell you minus be when I tell you electron Kulevi Sutta hey or we electron could they be Sutta hey lose be cursed I gain be cursed I take a to vote don't know but not a cat I am be an iron be here for H plus a H plus matlabu electron could be a hekey Lee I lose ki I key gain kiya plus at a matlabu lose karte touch plus a means it has loose its electron and below it is H-minus means it has gained here H-means it has gained one electron and it has become hydride ion similarly kids next topic is polyatomic ion, it has become monoatomic ion such ion which has only one atom, single atom polyatomic means there will be more than one atom group of atoms will be there such ion When you see it, you will see that it has more than one atom Means it has more than one atom in the ion If you see the formula, if you see the example, you will understand it well Okay, like first definition Before definition, I will show you this See this NH4+, NH4+, ammonium ion Name is ammonium ion, okay This is a cation type, obviously making a plus. Why is this polyatomic? Because, if you look carefully, in this ion, are there more than one element of atom? There is nitrogen and hydrogen. That's why it is called polyatomic. Polyatomic means that a group of atoms will remain and they will have an overall charge. This is NH4. I will write it down and show you. Overall, they will have a charge. Where is the paper? See, before this you were reading monoatomic, if I write Na+, it means sodium is an ion, right? If I write NH4+, it does not mean that plus charge is only for hydrogen, it is also for nitrogen overall and for 4 atoms of hydrogen it is a complete plus charge. Understood? So this is polyatomic because this ion has a group of atoms whose overall charge is 1. So this plus charge is 1 charge. That's why it is called overall charge Understood? It is same as hydroxide ion Hydroxide ion OH-OH-remember all these The more you practice, the better you will remember You have to practice all these We write OH-on hydroxide So this is OH-Its charge is minus 1 So here I have written OH-Question will come? It will come like this Tell me Is OH-ion a polyatomic ion? So you will write yes or no. So yes will be why? Because it has more than one atom and its overall charge is minus 1. Means the overall charge of both O and H is minus 1. Now I am just showing you. Nitrite ion, the formula of nitrite ion is NO2-. NO2, one nitrogen atom, two oxygen atoms and overall charge is minus 1. Similarly nitrate is NO3-. bicarbonate HCO3-charge is minus 1 sulfate ion SO4 2-remember all of these sulfite is SO3 2-carbonate CO3 2-phosphate PO3 3-PO4 3-phosphate is PO3 3-so the minus you see above 3-3-2-all of these are its charge and here is PO3 how will you write this? if I talk about phosphate So, PO4 3-. Like this. There is 1 phosphorus atom and 4 oxygen atoms. And overall their charge is 3-. Let me talk about carbonate. Carbonate is written here. CO3 2-. Means CO3 and their overall charge is 2-. So, these come only in polyatomic ions. So, kids, this is your first part. We will study in the second part. How to write a chemical formula of a compound. How will we write the chemical formula of any compound? This topic is very easy. Once you understand, no one can cut your marks. This is the thing.

For a long time, kids were requesting for this chapter. So kids, I am also involved in math, math mastery and other chapters are also being made. So it took a little time for that, sorry.

And before starting the video, let me tell you something about math mastery. Recently kids, what can I say recently? Yes, you can say recently. It must have been a month or even less than a month, we have launched Maths Mastery for you all, for Class 8 students. In Maths Mastery, every chapter of Maths is being explained very well.

I have bought the course for the children, it is an affordable course, the children who have bought the course and who are watching now, they know that every chapter is being explained very well. I had also asked the children for contents. So our contents are exactly the same. Like many kids have sent me their contents and I am making videos according to that.

And as the kids are getting requests, that first make this chapter, first make that. So according to that, they are getting the video. If you still don't know anything about Maths Mastery, then the link of that is given in the description box. If you also want that your Maths becomes strong, basic Maths is clear, concept is clear, doubts are clear, So you must take Maths Mastery, you must watch the video and if you like it, you must purchase the course.

Now without wasting any time, let's get started with the video. Okay, so Language of Chemistry. See, you have read this chapter of Language of Chemistry in class 7. So a lot is related, kids. For example, if you are reading about symbols, you will read about the same as the name of the word.

Because you have already read about the symbols. Then you will read the same chapter in class 9, where you will read about the symbols in detail. You have read in class 7, 8 and 9 also, but you will read in more detail.

So I am trying here. I will explain you as much as I can in important notes Because I have given a very limited book You will also see notes, I will tell you a lot of things You just keep a copy pen while noting down The important points you will find You will note down the important points and keep going It is going to be very useful, children It is going to be very useful So without wasting time, let's quickly read what is given in this chapter. First of all, see the symbol. What is a symbol? You all know.

What is a symbol? If we talk about the symbol of elements, then what are the symbols of elements? The symbols of elements are their letters.

Their letters. How do letters mean? One or two letter abbreviation of the name of an element. Like the name of an element.

Whatever the name is. Suppose I am talking about hydrogen. So hydrogen has either one letter.

or there will be another element which has either one or two letters we write abbreviation in short form we short the name of the element short the name of the element we give a letter or two letter one that becomes their symbol so you have already read the rules of symbol in class 7 we are not going to read about it at all ok, one minute so symbol you see one or two letter abbreviation of the name of an element or short hand abbreviation of the name of the element we call it the definition of symbol now if I talk about hydrogen then what is the symbol of hydrogen? H we have taken first letter of hydrogen and that too in capital for carbon we have taken first letter C and that too in capital mentioned in capital similarly calcium, c-a-l-c-i-u-m, calcium, what is the symbol of calcium? first and second, first two letters, first is in capital and second is in small, for boron it is b, so you know what are the different symbols, you have to do atomic number 1 to 20, you know atomic number, Atomic number from 1 to 20 starts with hydrogen and ends with calcium. What ends with calcium?

It has gone to 118. You have to remember till class 10, till 20. So you have to drink the atomic number properly. Drink the atomic number after mixing it. In that, you have to remember in an orderly fashion that after hydrogen, helium comes.

Helium comes after Lithium Then their symbols are also important If you don't pay attention to all these things, then there will be a lot of problems So their symbols are also important Like Ca is for Calcium H is for Hydrogen Ba is for Boron If your teacher asks you about any symbol, then you can tell them quickly Be for Beryllium C for Carbon N for Nitrogen So you should remember all these symbols too Ok So you know about the symbols, you have to remember all these Now the new topic for you all, maybe someone has already read about it, but I am sure many children do not know. This is a new topic, Valency and Valence Electrons. It is very simple and very important.

Listen carefully to understand it. It is very simple. If you understand it once, then there will be no problem. Ok, so Valency and Valence Electrons.

First of all, we will read about Valence Electrons. Then we will go to Valency. Ok, so what are Valence Electrons? What are the valence electrons?

See children, as you all know that one atom has many shells are there or not? like here in front you can see oxygen I will show you by making it if I make it in front of you then you will understand more I feel like this see, as we are talking about oxygen so I know the atomic number of oxygen 8 is there ok, you know 8 is there now write its electronic configuration This is called electronic configuration So how much oxygen is there? First goes 2 which you have already read Then 2 out of 8 goes and 6 is left So in the second you fill all 6 electrons This is done So what is its valence shell? Valence shell means last shell So in oxygen, the last shell is K So what is mana?

I will call this shell as last shell or valence shell Now you guys skip the word last shell Remember all these words valence shell So valence shell we call the last shell Last shell in which the electron has gone If I see its atomic structure, atomic model So this is our nucleus This has become the first shell How many electrons in the first shell? 2 electrons Then we made the second shell How many are there in the second? 1,2,3,4,5,6 So here this is valence shell, it is L only.

It is L only, its name is L. We got to know about valence shell. Now the electrons in valence shell, the electrons in valence shell, we call them valence electrons.

Valence shell means the electrons found in the last shell, we will call them valence electrons. Did you understand? What will we call them? Valence electrons.

so how many valence electrons are there in oxygen? see how many valence electrons are there in the last shell? 6 there are 6 electrons in the last shell so how many valence electrons are there in oxygen?

6 valence electrons did you understand? if you understood then that's it by the way if I talk about magnesium if I write the electronic configuration of magnesium then it will be 282 if you don't know how this thing happened I have made a video of atomic structure of the first chapter of this you must watch it, it is very important I have already told you about it that means this is not the first time for you this topic is not the first time for you I have already taught you but if you don't know how to decorate electrons then you won't understand this first clear it then watch this so magnesium has K L M electronic configuration 282 I can make it like this so here is the last shell we also call it outer most shell Last shell is also called valence shell and outermost shell. Both are the same name.

Don't get confused. How many electrons are there in the last shell? There are two. You can see it here. You can see it from here.

There are two. So in this case, how many valence electrons are there? There are two.

In the exam, the question comes. Tell me, how will it come? Will it say?

It will say like this. How many? If you want, then note down quickly.

How many valence electrons are there in nitrogen? Like this. How many valence electrons? are there in nitrogen it gives such a question it will definitely give or the number of valence electron in nitrogen is dash it will give like this so it is very important for you to remember the atomic number see how everything is related so in nitrogen it is 7 Atomic number KL First is 2, second is 5 First is 2 electrons, second is 5 electrons It will come like this So how many electrons are there in the last?

5 So how many valence electrons are there? Answer is 5 So the concept of valence electron is clear According to me there should be no doubt Now it is valency You must have read the definition of valency separately. This is combining the capacity of an element. The capacity to combine an element with another element.

The capacity to make a bond. The capacity to combine. This is called valency.

But this is the definition. This is its actual definition. This is what we understand. This is a big deal.

But this is what you will understand. Now see what is valency. Okay. So. It is the number of electrons an atom can donate or accept to form a chemical bond with another atom.

I will explain this with the help of an example. Here, suppose there is an element. Leave the novel gases and I am talking about the other elements. Now, the element will have an atom in it.

And you must be knowing that an atom makes a bond with another atom. Do you know one thing? Many elements make a bond with each other That is why many compounds are possible If I talk about water, H2O Hydrogen atom and Oxygen atom Hydrogen is one element, Oxygen is another Both of the atoms have made a bond That is why this compound is made Similarly, the salt you eat, NaCl NaCl, Sodium Chloride Sodium, Na is an element Chlorine is another element If we make a bond of both atoms, then a compound is possible. So remember that different atoms or different elements always try to combine with each other to make a number of compounds. Only then compounds are possible, otherwise compounds are not possible.

Otherwise compounds are not possible. Remember that. So when these atoms or elements come together and combine with each other, when they form a bond, So, there are electrons involved.

That means, electrons participate in the production of bonds. When a bond is made, the main work of electrons is done. Remember this.

So, when a chemical bond is made with one atom and another atom, how many electrons are involved at that time? What happens is, one atom either donates or accepts the other. That means, out of two bonds, Basically, one atom will give its electron and the other will accept the same electron.

Meaning, one will donate, lose and the other will accept it and gain it. So, how many electrons are losing or accepting? That is valency.

So valency means it is the number of electrons an atom can donate or accept to form a chemical bond with another atom. When one atom forms a chemical bond with another atom, then the number of electrons it is gaining or donating becomes its valency. If you understand it from the example, then you will understand it better. For example, Sodium.

Now you don't know whether sodium gains or gives electrons. You don't know this, I will tell you what it does. But for once pay attention that sodium looses one electron, donates one electron to the other. It can't take one electron. Sodium gives one electron.

So its valency becomes 1. If I talk about magnesium, do you know how many electrons it has? When it makes a bond with someone, it looses two electrons, it gives them to someone, it donates them. So if you give two electrons here, then its balance becomes two. Did you understand? Similarly, if I talk about oxygen, do you know what oxygen does?

It gains electrons, accepts them, takes them. This accepts electrons. Do you know how many electrons it accepts? It accepts two electrons. So when this makes a bond with someone, it takes 2 electrons.

It accepts 2 electrons. What is 2 electrons? How many electrons? 2. So its valency is 2. Do you know what nitrogen does to how many electrons? Like nitrogen.

Nitrogen also accepts electrons. And do you know how many it takes? It takes 3 electrons. How many?

3. So its valency is 3. Did you understand? So when an atom forms a bond with another, then the amount of electrons it is giving or taking, becomes its valency. That is what becomes its valency. Understood? Now, as we have a very important thing here, which is not given in your book, like not given in Living Science, this is extra, ok?

And if it is given in someone's book, then it is very good. Now look kids, now I will tell you this, how will you know which element is given? Will lose electrons and which element? Will gain, will take electrons.

How will we know? So remember, the metals, metals always lose electrons, give to the other person. Always.

Means the work of metals is that it gives electrons. It always loses electrons, donates, gives. But now the question is, how will you recognize if an element is metal or non-metal?

How will you recognise it? It is a very easy way to recognise it. The last cell, the valence cell, has either one electron, two electrons or three electrons. In which? In the last cell.

We are not talking about the previous cell, we are talking about the last cell, the outer most cell, the valence cell. So, the metal always has either one, two or three electrons in its last cell. So if you write electronic configuration like this then you will easily recognize it Like I told you about sodium a while ago I told you that sodium's work is to lose electrons So children, I will tell you that will sodium lose or gain Or you tell me what is sodium metal So you will remember the atomic number of sodium and write it Write electronic configuration Now see the last electron How many electrons are there?

One. So metal has either one electron outside, or two, or three. In the last shell. So you will recognize that it is metal.

And metal always, always loses its valence electron. It will always lose its last electron. It means it will never bond with anyone.

So its valence electron, the last electron, it loses it. Remember. So this is how you can find out. So here, you were reading about valency a while ago.

That the number of electrons an atom is donating or accepting, we call that valency. So here, sodium will lose one electron. Because there is only one electron in the outer most shell.

So the number of electrons in the outer most shell, will donate that number of electrons. Because it is metal, its job is to donate. so the electrons in the outer shell will give to the electrons in the valence shell so it has one electron so it will give one electron to someone and then it will make a bond so much clear and after making a bond and after giving electrons, you know there are changes in them in metals, after giving electrons, after losing them, there are changes a charge comes on them positive charge positive charge comes on metals when? When they give their electrons and then we call them cation. Means when they get positive charge, then we call them cation.

What do we call cation? Cation, cation. What do we call cation? Remember cation.

Okay. Now as if, now as if. Okay, it is here. It is here. After that I will tell you another example.

You must be able to understand, right kids? It is very simple. Now again take sodium.

Sodium atomic number 11 is written in electronic configuration 2, 8, 1 So how many electrons are there outside of sodium? 1 electron This is metal You have to first find out whether it is metal or non-metal We have not studied non-metal yet First you have to find out whether it is metal or not So you will write its electronic configuration You see at the end it is 1 that means it is metal And what does metal do? It leaves out the external electrons. How many electrons will it leave out? As many as it has outside.

Okay? As many electrons as it has in its last shell, it will leave out the electrons. The people inside do not participate. The electrons inside do not get loose.

So sodium has one electron, so what will it do? The last one electron will lose one electron. When it makes a bond with someone, it will lose one electron.

So if I make sodium here, KLM, there are three shells, so I made three shells. Two in the first, eight in the second, and one in the last. Okay, this is sodium, Na. After that, if we see how many electrons it will lose, it will lose one electron because it has only one electron outside.

So it will lose means this electron will go away from it. So what we will do now, we will see here. The last one has gone, so the first shell is there. In the first shell, there are two electrons.

Now this second shell, how many children are there in the second shell? 1, 2, 3, 4, 5, 6, 7, 8. Now I don't have to make the last shell because it has left its electron. so when it leaves the electron, it will create a positive charge on itself so when it releases the electron, it will get a positive charge on itself so you made it that it left one electron, see here there were three shells in the last shell there was one electron but here it is not made in the last shell because it has left one electron so it will get a positive charge So we give a bracket and write plus here. Here I have written only plus, that means plus 1. If I had written plus 2 here, that means it would have left 2 electrons.

But does it have 2 electrons outside? No. It left 1 electron, so it is only plus. Plus means plus 1. So this is Na, which means plus charge on sodium.

Plus means that it has a lack of an electron. Remember, I have written Na plus here. Na plus means that it has released one of its electrons.

Did you understand? It has released one of its electrons. So, see this line too. On losing one electron from the last shell, after losing the last shell or electron, it acquires plus one positive charge. On sodium, plus one.

I have not written one here. The meaning is the same. On this, plus one. plus one positive charge will come. So this is very important.

Very much. Similarly if I talk about aluminium first of all you have to know that aluminium as I will tell you, ask you will aluminium gain electrons or will it lose? So you first write its electronic configuration.

So you know the atomic number you know KLM 283 and write it see that in the last it has 3 electrons 3 are what does it mean it means it is a metal and if it is a metal then it will loose its electrons ok and how many electrons will it loose in the last how many 3 are so 3 electrons will loose understood so it will loose its 3 electrons so first of all I wrote its electronic configuration I saw that it is a metal and it has 3 electrons in the last shell so it will loose all 3 electrons after loosing all 3 electrons there will be a positive charge on the aluminium i.e. plus and I am writing 3 plus because it has loosed all 3 electrons did you understand? did you or not? if I talk about magnesium if I talk about magnesium I will ask you to tell me what is the condition of magnesium It means that there is metal, how will we do it? How will we know? So you will write its electronic configuration 282 So you will see in the last It is 2, that means it is metal It is metal means It will lose the electron, it will give And how many electrons will it lose?

How many are there in the last? 2 So it will lose how many? It will lose 2 electrons Understood?

It will give 2 electrons Means magnesium After giving 2 electrons 2 plus will be there. Because 2 electrons were lost, positive charge will come. But how much? 2 plus will come.

Aluminium was giving 3 electrons, so that became 3 plus. Understood? Now here I have written Al3 plus. Al3 plus means that Aluminium has a 3 electron deficiency. This means that, like I made sodium.

Actually, how is sodium? It is like this. 2 8 and 1. This is sodium.

2, 8, 1. K, L, M. Actually, this is what happens. But we know that sodium will lose its external electron. So how will it look? 2. 1, 2, 3, 4, 5, 6, 7, 8 and it will have 8 plus charge that means it will be 2 and 8 just 2 and 8 is K and L so guys, in sodium it actually remains like this ok, in sodium it actually remains 2, 8, 1 but now it has loosed one electron so it became 2 and 8 that means now this Na plus how much electron is missing in it? actually it had one electron extra but Na plus means there is a deficiency of one electron AL3 plus means that Al has a deficiency of three electrons Ca2 plus means that Cal has a deficiency of two electrons did you understand?

is it clear? and if I tell you about valency here we were talking about metals earlier ok so metals lose as many electrons as it has outside how many are there outside? either one is or 2 or 3 so outside of it, in the last shell, all the electrons of the metals will be its valency remember, I will teach you further that in metals, in the last shell, all the electrons will be its valency so if I talk about aluminium, I will ask you, tell me how much is the valency of aluminium so you know that it is metal, you write it down you will see that in the last shell, there are 3 electrons so the valency is 3 its valency is 3 in matter it is like this in last shell it will be like this in calcium last shell has 2 electrons so its valency will be 2 there is an exception case exceptional cases if i talk about exceptional cases then hydrogen, hydrogen is different outside of hydrogen it has only one electron and outside of it there is only one you will say that this is not metal yes kids, hydrogen is not metal it is non-metal, this is an exceptional case that outside it there is one electron but it is non-metal ok, helium this is the electronic configuration of helium outside helium there are two electrons but kids this is noble gas not metal, keep writing helium is noble gas, not metal that you will say that helium will loose two electrons, noble gas does not do anything neither accept nor loose and boron boron has two and three boron has three but it is not metal it is a metalloid we will study metalloid later these are exceptional cases you can see that this has one, this has two and this has three the nature of this is matching like a metal because we have studied that metals have one, two or three Here it is the same. But these people are not metal. Are they metal?

Not at all. These are exceptional cases. Take a screenshot. Now let's talk about non-metals.

Now how will we know if an element is non-metal or not? How will we know? Now how will we know if an element is non-metal or not?

So kids remember, outside non-metals, The last shell will have 5, 6 or 7 electrons Where? In the last shell If you take any non-metal name You know that oxygen is a non-metal You must know this You don't know? You know it right?

You know that oxygen is a non-metal If I make its electronic configuration It will be 2,6 Nitrogen is also a non-metal I am showing you by making it. Now see these three cases. If any element is non-metal, then its outer most shell, the last shell, should have either 5 electrons or 6 or 7. You will say, why did you leave 4? You took 1, 2 and 3 in metal.

You took 5, 6 and 7 in non-metal. Why did you leave 4? Like carbon.

K, L, 2 and 4. Children, okay, carbon is also non-metal. But, its case is different. You will study in class 10. I will tell you.

I have written somewhere after this, exceptional case. What is there, what is not. So, once you leave the 4 one.

When you go to higher classes, take it in 9th. In your concise, I have concise. Where did it go?

It is not here. In 9th, you buy concise book for chemistry. Conscience, it is of Selena. Selena publisher.

I have noted down the details in the notes on the side. You will read the full actual in the 10th. Not now. So you can see that if there is a non-metal element, then outside that there will be 5, 6 or 7 electrons.

What does non-metal do? The nature of non-metal is that it will gain electrons, accept them, take them. What did metal do?

It was giving. Non-metal will always gain electrons. Non-metals gain electrons.

And after gaining, they get minus charge. What does that do? What was coming on metal? Positive.

And what comes on non-metals? Negative. And when they get a negative charge, we call it anions.

What do we call it? Anions. What do we call it?

Anions. Did you understand? So here you are seeing that these three, oxygen, nitrogen and fluorine, these three are non-metal. So what will these three do?

They will gain electrons, they will accept electrons. Their nature is that they accept electrons and after accepting electrons they get minus charge and after getting minus charge we call it anion like after getting positive charge in metal they were called cation now we will call them anions now let us read the example of chlorine ok now What is chlorine? I will tell you about oxygen. Now, let's see about oxygen. Now, children, you have seen that oxygen is non-metal or metal.

It is 6 outside, that means it is non-metal. It is non-metal, it is clear. What does non-metal do?

It takes or gives electrons. It will gain or accept electrons. Remember, what will non-metal do?

It will gain electrons. But the question is, how many electrons will it gain? How many electrons will it gain?

How will we know? There is a formula for this. What is the formula?

8 minus valence electrons You have to know how many electrons it will gain So what you have to do is, 8 minus valence electrons How many are there? 6. That means 2 That means it will gain 2 electrons. How many electrons is it taking? 2 electrons. Now After taking 2 electrons, see outside 2 will come, then 8 will come.

So, kids, you guys remember one thing. You guys have heard of the name of noble gas, right? Noble gas is absolutely amazing. It lives like a king.

Do you know what? Like a king doesn't do any work. It doesn't mean that they will be busy all day.

They will be busy all day. They live their life in a comfortable way. Okay? Positive way. They live their life in a comfortable way.

Similarly, noble gas, these noble gases have a total of 6 elements. These six elements are very stable. They are not related to anyone.

They are lazy and live in comfort. They are not related to anyone. So, apart from the noble gases, all the other elements like oxygen, hydrogen, etc. are irritated by the noble gases.

They wish they could become noble gases. They wish they could live like them. They wish they could be stable like them.

Do you know why these noble gases are stable? Because the outer most shell of these, if I talk about these, take Argon for example, look at their electronic configuration, 288. Neon, this is also a noble gas. Take this one, 28. So the last shell of this, look, all of them have 8 electrons in the last shell. Where the last shell has 8 electrons, it means it is stable, not just a small one.

They will become absolutely stable. So all the other elements think that we wish we had 8 electrons outside. They wish, they all think. And somehow they bring 8 electrons. How do they bring?

By making a bond. They make a compound by making a bond with each other. In that case, they also get 8 electrons outside.

Means they want to be stable. So all the elements see that which noble gas is near us. I can make the noble gas that I have.

Did you understand? And in noble gas, helium is the only exceptional case, outside of which there are two electrons. And this is also stable.

It is not that it is not stable. In the case of helium, this is also stable. Outside of it, it has two total electrons. So this is also stable. But the remaining noble gases in the last shell are of 8 electrons.

How many? 8 electrons. where 8 comes means Jai Ram ji that means we live very comfortably so all the other elements think that we should also become stable like the noble gases that are near us so this oxygen also wants to be stable so as I was telling you that it will gain because it is non-metal so how much electron will it gain? it wants that the noble gas near it is neon because its atomic number is 8 and its atomic number is 10 so this means that I have 6 electrons in the last cell and I take the electrons so I also make 8 electrons in the last cell so how many electrons will it take to take 8 electrons in the last cell?

2 electrons. That is why I told you the formula 2 electrons are not coming out of the formula so why is it taking 2 electrons? so that it becomes stable so that the last cell becomes stable so how many electrons will it take?

2 electrons If I talk about valency, then how much electron is this oxygen gaining? If you see the definition of valency, then what was there in valency? Number of atom except, means number of electron accepts an atom. So here oxygen is...

to stabilize you, how many electrons are you accepting? How many electrons are you taking? 2 electrons are you taking.

So the balance of oxygen is 2. Now you understood what the balance of oxygen is? 2 came. Means 2. The balance of oxygen is 2. Understood?

And after taking the electrons, look carefully. This will take 2 electrons, oxygen. After taking the electrons, they get a minus charge.

What charge? Minus charge. Now look here.

As this is oxygen, I made 2 electrons in the first shell and how many are there in the second shell? 1, 2, 3, 4, 5, 6. This is normal oxygen. What will it do?

It will gain 2 electrons. It will take 2 electrons. So let's give it 2 electrons. It will take 2 electrons.

Here it was KL, here it is 2. And if it takes 2, it was 6, so... and if it takes 2 electrons then it will take 2 electrons in the same shell see kids, it will allow to take 2 electrons in the last shell it is not like it will take 2 electrons in the inner shell it is not like that it will accept 2 electrons in the last shell so in the first shell it was 2 electrons in the second shell it was 6 electrons 1,2,3,4,5,6 and how much it took? it took 2 electrons so it will take 2 electrons in the same shell now see it became stable and after taking 2 electrons, it will get minus charge but how much minus will it get? 2 minus how much?

2 minus because it has accepted 2 electrons so 2 minus charge will come in it understood? sure? and we will call it anion hey kids there is a lot of it if you go inside there is a lot of things here we have talked about chlorine chlorine has 7 valence electrons how?

let's see how do we know? if you don't remember the atomic number then you will get stuck you guys remember this thing understood? we also remembered the atomic number but it is easy it happens KLM 287 So the electronic configuration of chlorine is 287 Remember this Remember this, this is something to understand Now Now see if this is metal or non-metal So in the last shell you see 7 So outside non-metals either 5 or 6 or 7 is there So this is non-metal What does non-metal do?

Gains electrons So this electron will gain Now Question at a kitna gain karega to formula care eight minus last me jitte be electron hotel to eight minus seven that is one They could they electrons gain karega one electron gain karega Agar ye one electron gain karega its kavalency kita o jayega one o jayega Samajh me aaya to me upper chlorine banati you pala shell me head to up long at chaser pencil seven Anna Dusra me hey eight or lash me kitna seven so one two three four 5, 6, 7. This is done. Now what is chlorine doing? It is accepting 1 electron.

We have read it. So when it will accept 1 electron, where will it do it? It will do it in the last shell. It will do it in the last shell. It will do it in the last shell.

It will do it in the last shell. So in the second, 2. Sorry, in the second, 8. In the last, how much was it? 7 was there.

It was like this. But if it will accept 1 more, then 1 more will come. That means 8. If it accepts 1 electron, then it will get charged. one electron is accepted, so minus one here minus, this will be Cl minus this was chlorine but this is Cl minus you understood, this is chlorine and this is Cl minus so it is like this, you can do it easily like this you can do it very easily, I left a space here to make it, let's make it chlorine has a normal electronic configuration of 287 so here 2 electrons are there, here 8 and here 7 but if it is accepting one electron if it accepts one electron then instead of 7 it will be 8 and this will be Cl-so in first we will put 2 In second we will put 8 In third we will put 8 And this will be CL-Put it like this Ok Let's talk about oxygen We have already read all these things Let's talk about oxygen So in oxygen Normally in last See 6 electrons This is non-metal So this will gain electrons Now the question is How many electrons will it gain?

So 8-6 is 2 So it will gain 2 electrons and that will be its valency. How much will its valency be? Its oxygen will be 2. Let's add here. First is 2, second is 6. 2, 2. O2 minus, now see it gained 2 electrons.

So 1, 2, 1, 2, 3, 4, 5, 6. And it gained 2 electrons. So it became 2 and 8. Now after gaining 2 electrons, it will get charged with 2 minus. Means, after gaining 2 electrons, this is 2 minus.

If it would have done 1, then 1 minus. But it will not do 1. It will gain 2 electrons. Now it has to become 8. Isn't it?

It had to bring 8 in the last turn. Is this clear? Now see this thing. I have already told you that all the elements, they all want that like their past noble guests, their electronic configuration should also be done.

Means in their last shell 8 electrons should come I have already told you about noble gases So you can see here See I have already told you about this thing But I didn't write it there so I will write it here If you want to know the valency of metal So how do you know the valency of metal? Number of electrons in the last shell In the last shell, the number of electrons will be the valency If we talk about sodium then 281 This is metal, sodium definitely. So if someone asks its valency, what will you see? How much is there in the last shell?

There is one electron, so valency is 1. Magnesium's electronic configuration is this. How much is its valency? How much is there in the last shell? If there is 2, then valency is 2. If there is 2 in calcium in the last, then valency is 2. So you have to find the valency of metal. Just look at the last shell.

The amount of electrons in it will be its valency. Similarly, how will we find the valency of non-metal? 8 minus number of valency electrons.

If someone asks for the valency of fluorine, then the electronic configuration of fluorine is KL, that means 2,7. Fluorine has 9 atomic number. So electronic configuration is 2,7. If someone asks for valency, then don't put 7 here.

If you put 7, then it will be wrong. This is non-metal. The formula of non-metal is this, to get valency. 8 minus number of valency electron. So 8 minus 7 is equal to 1. Similarly, chlorine's again 8-7 is equal to 1. Nitrogen's 8-5 is equal to 3. So its valency will come out like this.

Some exceptional cases here, yes, see this, non-metals. Now we had read that outside non-metals, either 5 or 6 or 7 are there. Carbon is a non-metal, outside that 4 is there, but I did not write that here. Actually, what happens, children?

The carbon that is present, it does not gain any electron because it is non-metal. This carbon is non-metal. So, should it actually gain or not? It should. But what does carbon do?

If it takes electron from someone, then it has to spend a lot of energy. Meaning, the use of energy there is very dangerous. So, the carbon thinks that I don't want to take electron at all, I will not keep this mess.

So, Carbon shares its electrons with everyone. That's why we don't write 4 electrons. Because we will share the rest.

There are different cases in higher classes. You have to remember this. That's why I wrote 5, 6 and 7. But in the case of carbon, there is a lot of energy.

Energy is used a lot. Energy consumption, energy consumption. What does carbon think about this? that I will not take from anyone, I will share my electron with someone. This was an exceptional case.

Now in your book, This topic is given. What is Variable Valency? As you all know about Valency.

We have studied Valency a little while ago. How to find out about metals and non-metals. Similarly, it is Variable Valency.

Variable means more than one. More than one. Variable Valency means more than one valency. Like a person has one car. Think like this.

Everyone has one car's rule. Okay. But there are some people who have more than one car So suppose here there are many elements and metals Which have one valency But there are some metals which have more than one valency That is what we call as Variable Valency Now children to understand Variable Valency You have to see this diagram first and understand Like this is an atom Here I have made 3 shells according to my own Now We know that normally when we extract valency or for valency, who is responsible? Valency electron.

We have read that valency electron is responsible for valency. Okay. So, you have read that metals and non-metals, metal loses all the electrons outside. That is its valency. Non-metals take electrons to aid outside.

They take electrons. That is their valency. But one thing you have to keep in mind is that anytime, any element, any metal or any non-metal, if it is loosing an electron, then it will loose its last electron. That means the outer valence electron.

If any element is taking electron, non-metal, if it is taking electron, accepting it, then it will accept in the last shell. So normally, for valency, these last shell electrons are responsible. Now if I talk about metal, because in your course it is related to metal. Metal will always lose electrons from the outer shell. Because you have read, metal works to lose electrons.

What does metal do? It leaves electrons, loses them. So metals always lose their valence electrons. They always lose them.

they will loose the last electrons here and that is why we know about their valency but there are some metals like this some metals like this that you know what they do they will loose their last electrons but with that just last one we call it penultimate cell Means they loose electrons from their valence shell along with their penultimate shell. Why do they do this? Because they are not stable. There are many more reasons.

You will learn about this in class 11-12. But if teacher asks you that in this case electrons came out from last shell but why they came out from penultimate shell also. Means why they came out from just inner shell also. So you can say that ma'am maybe to get stable or to get stability.

to become stable, to become stable, they are releasing electrons from the inner shell when this happens, then only the metals get more than one valency now did you understand? normally all the metals, what they do is, they release electrons from their valence shell means they loose their valence electrons that is how they get their valency but there are some metals which will release from their valence shell Along with that, they also release from their penultimate shell. Because of that, they get to see more than one variable valency.

Like copper. Now this is copper. Copper's symbol is Cu. Copper shows two valencies, one 1 and one 2. Copper shows two valencies, one 1 and one 2. Means, see here there is more than one valency.

Now, if copper here plus, means, plus 1, I have not written 1, let's write 1. If Cu plus is shown to you, that means it has released 1 electron. Is it or not? You must know this.

And if you see Cu 2 plus, that means copper has donated 2 electrons. It has donated. Remember this. If Cu plus is there, that means copper has donated 1 electron and released it. And if Cu 2 plus is there, that means copper has donated 2 electrons.

So the name of Cu plus, we call it cuprous. CU2 plus is called cupric. Its name starts with its Latin name.

It is called cuprum. Now, one of these two is small valency. So, the suffix after it is OUS.

So, cuprus. And this two is big. So, RIC. RIC is used. This was new.

I added extra. If it is in someone's book, then it is good. If it is.

Iron also shows more than one valency. Iron has two valencies like 2 and 3. Let me tell you one more thing. I didn't tell you. I have written it here.

I have written it in Roman number. I will tell you this. Now, as we know that copper has two valencies. That means copper shows more than one valency.

Now, if it is written like this, copper and bracket in Roman number is 1. That means this is talking about Cu+. If it is written like this, copper and Roman number is 2. It will be written in Roman number only It will not be written in Hindu Arabic style Which we read 1,2,3,4 If you write it like that, it will be wrong Listen carefully to what I am saying If it is written in copper and in Roman number in bracket 2 is written That means that copper's valency is 2 And these people are metals So by losing the electron They obtain plus charge Okay, so it is 2 plus Similarly, iron Iron also shows two valencies One is 2 Where did it go? Where did I write?

Here it is and one is 3 Iron symbol is Fe What is the symbol of Iron? It is Fe Iron symbol is Fe Iron shows two valences, one 2 and one 3 If written by iron and in bracket Roman number has 2 written That means valence is 2 We will write Fe 2 plus If Roman number has 3, then Fe 3 plus like this name is written with Latin name so this is called ferus and this is feric this valency is smaller than 2 and 3 so OUS is in suffix ferus and here this is bigger than 3 that means feric remember this I have made a lot Now let's talk about lead. Lead symbol is Pb. Okay.

Lead also shows two valences. One is 2 and one is 4. If 2 is written in Roman number, that means 2+. And 4 is written, then Pb is 4+.

Similarly, mercury. Mercury 1, Mercury 2 That means Hg plus Hg 2 plus Mercury symbol is Hg Now it is 3 3 symbol is Sn 3 The symbol of 3 is Sn. This too again shows 2 valences.

One is 2 and one is 4. So if Roman number has 2, that means Sn is 2+. And here Sn is 4+. So kids, here we are studying only metals. Because here everywhere plus has come because these are metals.

Metals lose their electrons and obtain positive charge. That's why we have put plus with valence. If you see anywhere, there is a number with plus.

Like Sn is 2+. That means this 3 is... They have lost 2 electrons. You should know what the meaning of what you see here is.

Okay? SN4+. You guys note down this. It will be useful. SN4+.

SN4+, means the tin has lost 4 electrons. It gave 4 electrons. I don't know to whom, but it gave. Understood? Do you know what question comes in variable balance?

Why do some metals exhibit variable valency? Why do some metals have variable valency? So what is the answer to that? Why does it happen? The reason is because they lose electrons from valence shell as well as penultimate shell.

Did you understand? Because these people release their electrons from valence shell as well as penultimate shell. Now, Now kids we will learn about ions. Ions is a very simple thing.

What is it? See. You have read, right? Atoms give electrons. Some take electrons.

You have read, right? Some atoms, i.e. metals basically, which lose electrons, donate them. And some accept electrons. So when these people do this work, to take and give electrons, then they get a charge.

Or you can say, We will call them ions then. Like, look carefully. Atom, look carefully, open your eyes and see. Atom, if it is also losing electrons, I will write the symbol of electron. Atom minus electron means, when atom loses electrons, it becomes ion.

Or atom. plus electron means when atom gains electron then also it becomes ion understood? remember this thing when an atom loses electron or when an atom gains electron then what can we call it? then we call it ion then we call it ion then we call it ion ok and everyone knows about ion that ion is a charged particle ion is a charged particle means there will be a charge in the ion.

There are two types of charge, positive and negative. Now see, when an atom loses an electron, you have read about metal, right? When metal loses an electron, what happens? It gets a positive charge.

That means the ion here, what will be its charge? Positive. And when an atom gains an electron, it will also get a charge.

At that time, there will be a negative charge. and we have given it a name we will call it cation means when an atom loses an electron it becomes cation ok and when an atom gains an electron it becomes anion so here it is all the same the definition of ion comes when an atom loses or gains electrons it becomes a charged particle called ion you understood the meaning of ion now as you are aware that sodium is metal it loses an electron so it loses means it also becomes anion It will become a solid ion. So this is an ion. Ion means charged particle.

What will become? Charged particle. Now you know that if it loses, then it will get a positive charge. That's why we write it as Na+.

And we will call it cation. Similarly, calcium. Calcium loses its two electrons.

It is losing and it also becomes an ion. This will also become a charged particle. And how do we write it?

Ca2+. So this will become Ca2+. Similarly, chlorine is non-metal. So what is the work of non-metal to gain electrons? So chlorine gains one electron.

So here the atom is gaining electrons. After gaining, it will also become a charged particle. It will become an ion. And here it is gaining, so it will become Cl-If one electron is gained, then Cl-Similarly, nitrogen is again non-metal.

It will also gain. It will also take the electron, so it will also become a charged particle. And we write it as N3-Means we will write N and 3-Because it accepts three electrons.

So now if we look at it, then ions are of two types, cations and anions. Cations are of positive charge and anions are of negative charge. Question comes, what do you mean by cations? So what will you write? When an atom loses electron, It forms a cation.

Or cation is a charged particle. And cation is an... Or write it like this. Cation is an ion which is formed when an atom loses electron.

When an atom loses electron. You can write it like this. Similarly, what do you mean by anion?

How will you define anion? How will you define anion? Anion is a charged particle. Or anion is an ion.

Listen carefully. Anion is an... iron which is formed when a when an atom gains electron if you write it like this then it will be done and you should understand it is not like you will write the definition which I have said by writing it in a rata where you will understand you will frame the definition ok so see I have written here how iron is made when metal loses electron So metal loses electrons and becomes cation. Now how do we call this?

For example, Na plus. I will call this sodium ion. Because metals have no problem in writing their names.

When metals make cation, they have no problem in writing their names. Na plus is called sodium ion. Ca2+, where you will see plus, then understand that these are cation.

So how will you write their name? The name of Ca is calcium and iron. Al3+, aluminum name is iron. Similarly, write K+, potassium and iron.

If we talk about non-metals, then non-metals gain electrons. After gaining, they become anions. How do we write their name? As you have seen, this is anion, minus one. So behind their name, IDE is written.

Meaning, last one, its name is chlorine. But after NE, IDE is written. IDE is written, basically.

Okay? So, chloride ion, oxygen is oxide ion, bromine is bromide ion, N3-is nitride ion. There can be many such examples in your book. You can see them.

But we write names like this. Non-metals have an ID and metals have no problem. Write names and add ion. Similarly, children, there are two more categories in iron.

One is monoatomic and the other is polyatomic. Monoatomic iron and polyatomic iron. Okay, mono means one.

What does mono mean? It means one. Okay, so who is monoatomic?

Look carefully. Mono means one. Mono means 1 So if you are looking at an ion like this It can be a cation or anion It can be a plus, a minus or whatever it is Either it will be a plus or a minus So you can see something like this Write the plus and the minus Such an ion which will have only one atom One atom means the atom of one element Like Na+, this is just an atom of sodium Ca2+, this is only calcium N3-, this is only an atom of nitrogen O2-is an oxygen atom, Cl-is an chlorine atom, Al3-is an aluminium atom.

So all these ions that you are seeing, there is only one single atom in it. So we will call it a monoatomic ion. So see the definition.

An ion that consists of only a single atom with a charge. Meaning a single atom with a charge. So here is 3+, there is a minus, there is a 2-. Such an ion which is made up of a single atom. which is made up of a single atom we call it monoatomic ion there are many examples of monoatomic ion first you see the examples see how many examples are there all have one atom all have hydrogen, sodium, potassium, magnesium, calcium, copper, iron apart from that there is no other in one place, in one bar, there is only one atom only one element atom by the way there are also minus ones how many are there, all are monoatomic All the ions you see, plus and minus, all have single atoms So here we will see cation and anion So first of all hydrogen ion Cation means all will come first So we will give the symbol of hydrogen and put plus It is charged with plus one Sodium ion, Na plus and sodium definitely plus This is charged with plus one You all know that sodium loses one electron that's why it is made of Na+.

Similarly potassium loses one electron that's why it is made of K+. The symbol of potassium ion is ions. I am not taking the name of the element. These are not elements but ions.

So we can write potassium ion as K+. And its charge is plus 1. Magnesium ion loses 2 electrons. So it is plus 2. Similarly calcium also has look at the iron carefully in copper bracket, roman number has 2 it is like this, it can be like this too and it can be like this too so don't get confused in bracket, here is 2 so it means that it is talking about Cu2+, charge is plus 2 similarly iron has 2 in bracket that means it is talking about Fe2+, and plus 2 in aluminium ion, Al3 plus is there and this is plus 3 so these are the cations, monoatomic ones similarly if I talk about monoatomic anions here is the cation Similarly, if I talk about monoatomic anions, first of all, Hydride ion.

Hydride ion means hydrogen. See in the back, IDE, IDE, IDE is written. Hydride means H-. Okay? Valency means, it is charged, minus one.

Chloride ion, Cl-. Bromide ion, Br-. Iodide ion, I-. Oxide ion means, it is talking about oxygen, 2-. Sulphide ion means, it is talking about sulfur.

So, the symbol of sulfur is S. and its 2-that means it accepts 2 electrons here you are seeing here is phosphide ion, talking about phosphorus P is 3-that means here phosphorus has gained 3 electrons N3-nitrogen has gained 3 electrons sulphide S2-sulphur has gained 2 electrons and here is the charge now you will be confused here what? you will say madam here also hydrogen is there Plus may be hydrogen hey, yeah, but it's the Bachu hydrogen exceptional cases hydrogen.

Okay, hi doesn't know plus be when I tell you minus be when I tell you electron Kulevi Sutta hey or we electron could they be Sutta hey lose be cursed I gain be cursed I take a to vote don't know but not a cat I am be an iron be here for H plus a H plus matlabu electron could be a hekey Lee I lose ki I key gain kiya plus at a matlabu lose karte touch plus a means it has loose its electron and below it is H-minus means it has gained here H-means it has gained one electron and it has become hydride ion similarly kids next topic is polyatomic ion, it has become monoatomic ion such ion which has only one atom, single atom polyatomic means there will be more than one atom group of atoms will be there such ion When you see it, you will see that it has more than one atom Means it has more than one atom in the ion If you see the formula, if you see the example, you will understand it well Okay, like first definition Before definition, I will show you this See this NH4+, NH4+, ammonium ion Name is ammonium ion, okay This is a cation type, obviously making a plus. Why is this polyatomic? Because, if you look carefully, in this ion, are there more than one element of atom?

There is nitrogen and hydrogen. That's why it is called polyatomic. Polyatomic means that a group of atoms will remain and they will have an overall charge.

This is NH4. I will write it down and show you. Overall, they will have a charge. Where is the paper?

See, before this you were reading monoatomic, if I write Na+, it means sodium is an ion, right? If I write NH4+, it does not mean that plus charge is only for hydrogen, it is also for nitrogen overall and for 4 atoms of hydrogen it is a complete plus charge. Understood? So this is polyatomic because this ion has a group of atoms whose overall charge is 1. So this plus charge is 1 charge.

That's why it is called overall charge Understood? It is same as hydroxide ion Hydroxide ion OH-OH-remember all these The more you practice, the better you will remember You have to practice all these We write OH-on hydroxide So this is OH-Its charge is minus 1 So here I have written OH-Question will come? It will come like this Tell me Is OH-ion a polyatomic ion?

So you will write yes or no. So yes will be why? Because it has more than one atom and its overall charge is minus 1. Means the overall charge of both O and H is minus 1. Now I am just showing you.

Nitrite ion, the formula of nitrite ion is NO2-. NO2, one nitrogen atom, two oxygen atoms and overall charge is minus 1. Similarly nitrate is NO3-. bicarbonate HCO3-charge is minus 1 sulfate ion SO4 2-remember all of these sulfite is SO3 2-carbonate CO3 2-phosphate PO3 3-PO4 3-phosphate is PO3 3-so the minus you see above 3-3-2-all of these are its charge and here is PO3 how will you write this? if I talk about phosphate So, PO4 3-.

Like this. There is 1 phosphorus atom and 4 oxygen atoms. And overall their charge is 3-. Let me talk about carbonate.

Carbonate is written here. CO3 2-. Means CO3 and their overall charge is 2-.

So, these come only in polyatomic ions. So, kids, this is your first part. We will study in the second part.

How to write a chemical formula of a compound. How will we write the chemical formula of any compound? This topic is very easy.

Once you understand, no one can cut your marks. This is the thing.

Transcript for:Understanding Chemistry Symbols and Valency

Transcript for:
Understanding Chemistry Symbols and Valency