uh good morning uh we are going to go over this chapter uh class media again this is a basic vocabulary we are going to learn in chemistry once we get to uh more uh complex or math involved situation where you will see the class videos where I work on the board okay here in this chapter the title as you can see chapter 3 elements and compounds so we are going to look into the elements and uh elements are arranged in something called a periodic table and then compounds basically are basically made from elements in order to make a compound you have to do a chemical reaction okay so that's basically what we are going to look at the title of the chartreuse elements and compounds so the next slide basically what we are going to see is what are we going to look at these chapter elements again as I said elements are building blocks of any matter so we are going to see how the elements are distributed and when we do the elements remember how do we name them or write the symbol for them okay symbols are very very important it's very Universal so when we write the symbols for K elements it is very important that we use the to use the very standard way of writing it okay and as I said elements are arranged in a table which we call it periodic table and then the periodic table we are going to look at them how the elements are classified classification is basically grouping how elements are grouped in a periodic table and then as I told you compounds are basically made from elements and then when we write a when we make a compound in a chemical reaction we have to write them uh there are two ways of writing them either writing them in English or we can write them in in terms of symbols okay say for example uh sodium chloride I can write it in English and also I can write it in a symbol NaCl okay so it's very important to know given a simple symbol you should be able to read the name and given a name you should be able to write the symbol both ways you should be able to do that okay so basically we are going to look at the elements how how we write I will how to name them and write the symbols the same way how elements are arranged in a periodic table and the last thing is we are going to see some compounds when we have a compound how do you write their formula very simple chapter this one it doesn't involve any any math a whole lot okay again like I said an element is a basically the fundamental substance and elements are basically like arranged in the periodic table and they cannot be broken down uh by any chemical means and remember even elements are made up of atoms if you are wondering about what's the difference between an element and an atom uh just think of a bag of sugar right if you have a bag of sugar you have granules of sugar so each granule is an atom so the bag of sugar is something called elements okay so elements are when I say elements or the building blocks of matter basically it is a way to build compounds when we do chemical reaction in a lab we do what is called a compound and elements are basically used to do that we're going to say pretty quickly that even within the elements we have atoms atoms are actually involved in a chemical reaction so elements when we say building blocks that's how you make compounds okay and then the smallest part of an element when you look at the element the smallest part is what is called atoms and these are the atoms which are involved in basically a chemical reaction okay it's the same thing the the anything which is a red item so these are some definitions I want you to pay attention to that uh it is very possible that you may be tested on this like what is an atom uh so so on and so forth okay so anytime when something is highlighted or colored it is very important that you make a note of it even if you look at the previous slide you see that this is basically making sure that it gets to your attention and then that way you know you have to pay attention to that part now if you look at this element on the most prevalent in the elements in the human body remember our body is made up of so many different elements the most important of the more oxygen which is 65 percent all right carbon is about 18 the rest of them are in a very very small amount so the the the most important element in our body is basically remember our oxygen like 65 percent and names of elements the next thing is we are going to look at the name when we look at the names uh of the elements some of the elements are their name is derived straight from English some of them are derived from Greek and Latin some of the examples are given right here okay so say for example iodine comes from the Greek word iodus okay so that's how the name will be so it is not like uh you see look at the sometimes it's very easy to write the names by just looking at the symbol you might think C is carbon true CA is calcium but if you see C you cannot say carbon for both so it is very important that you know the names and the symbol the same way sodium is n a but then the sodium symbol is Nea came from the word nitrium okay so some of the elements name comes straight from like we can write in English some of them is derived from other languages and let's look into a few examples here so this is how we write the symbol for elements each element has an abbreviation called a symbol now when we write the symbol it is very very important I am going to look at an example and explain to you later on when you write a symbol it is if a element's name has two letters the first letter must always be a uppercase the next one is a lowercase if it has only one letter it is basically an uppercase okay very important to understand and this is what is given here nitrogens formula is n now you might be wondering what is this number seven this is an atomic number we will get to that when we hit on that concept but for now remember if you if you have access to the periodic table you can look at them each periodic table has a small rectangular boxes where you have the symbols okay so nitrogen is n right here and if you see gold gold is not g so it is uh coming the symbol is a u it is derived like a aurum a u r a m but then that's a symbol for gold okay Au the point you have to remember is the first letter is written in uppercase and the second letter is written in the lower case so the next few slides are going to be pretty much the same it is giving the symbols for each one of them I may not have to go through each one of it but you can see that here what is so consistent on all this you all these elements have two letter symbol but then we always write the first symbol uppercase and the second lower case very very important with the exception of this one Boron boron has B okay so it's very important to know uh within the B you have so many elements here barium bismuth bromine and boron so some of them has one letter some of them are two letters it is very important to know if you have two letters the first one should be uppercase the second one should be a lower case okay and again if you can look at this one uh these are the elements again some of them you can see the name but it is derived from some other language so potassium is not p if you write p e p is phosphorus okay so potassium is K and silver is not s i silver is a g okay it's derived from another language if I write s i it is silicon there is an element called silicon so it's very very important that you write the symbol of course you will have access to your periodic table so it's not an issue at all so you should be able to write the symbol but the point you have to remember is do not write both letters uppercase okay a classical example we may end up with the later on I can show you uh something like C and O if I write a big c and a small o it's an element if I write Big C and Big O it is a compound you might think it may not be a big deal it is it is a big deal so you got to be very very careful when you think of a symbol okay um see these are derived sodium the same thing it is natrium and then tin is a metal which is SN it derived from the name stanum okay and then tungsten is basically W it is derived from this word right here okay so some elements names are pretty straightforward some of them will be derived from another language so you got to be careful here okay here we go just now I said this here um consider the element Cobalt Cobalt has this symbol C and O okay I want you to pay attention to this if a symbol is given like this if I give you the symbol ask you what is this this is an element if I give you a symbol like this both are uppercased it's a compound okay so that's an Evidence by looking at the symbol we should be able to see whether it's an element and a compound by the way what's the connection between an element and a compound compounds are made from elements okay so it is very important that when you write symbol it is universal you got to make sure that you write them correctly so here it is C and O Cobalt you've added this o is written in a small letter here it is in uppercase okay now the next one is uh is going to be so we have seen the same elements and what is the major the the major part of the element within our body okay and then we have also learned elements are the building blocks of making uh compounds and within the elements we have a smallest particle which we call atoms and what else we have learned elements uh basically when it has either a one letter or a two letter symbol it has two letter symbol we got to make sure that the first letter is uppercase the second letter is a lower case so okay now the next one is uh this is uh basically what the periodic table if you want to look at the periodic table it will look something like this right here uh something like that okay now here each color is different and then what they do is they have given it in uh in a they can be classified into a specific groups right here so this is actually what the periodic table is and I'm going to come back to this periodic table right here as you can see that this the number there is a number on the top and there is a symbol right here okay so this is how elements are there then when we have the elements in the periodic table we are going to separate them in other words they are we are going to classify them okay one is what is called a general classification another I what it called a main group or representative elements there are two types of classification of elements in the periodic table okay one of them is basically a very general classification the other one is group voice especially there are four main groups which are involved in that okay so I'm going to come back to this here these two slides there is one group which is called noble gases but let me give you the general one here okay so if I look at the uh these are some of the groups have a specific names so we need to remember first of all let's see what is in a periodic table in a periodic table when I go from top to bottom right here okay these elements we call them a group okay the top to bottom when from up to down if you go down in a particular column we call it a group when I go from left to right I call it a period p e r i o d period Okay so the top one from top to bottom is group the left to right are periods okay no so what is so special about the group remembering in most cases the majority of the cases uh all the elements in a particular group they will behave the same way okay so they will have the same reactivity there may be some exceptions to the rule but in general if you look at all the elements in your group what are the group this one is a group right here this is another group from top to bottom okay so these are all uh basically what is called groups now a general classification of General classification means classification is basically a grouping okay so the general classification of elements in a periodic table the either they are metals metalloids and non-metals now remember I'm going to stay on this slide for quite some time but whatever I explained also is given in the later slides okay so you are going to read the same thing so I'm going to stay here for a few few minutes but the later slides basically is going to reflect what I said all right so the top to bottom is groups the left to right is periods okay now if I look at the elements in the periodic table they are metals non-metals and metalloids so what do you mean by a metalloids metalloids or basically metalloids or the elements which shows that characteristics of both metal and a non-metal very important to understand okay and so if I look at this one majority of the elements in a periodic table they are metals you can see that there are totally like 118 most of them like about 80 to 90 of them are naturally occurring and in general if you look at them um majority of them elements or Metals right here metals are colored like this usually metals are if you look at this periodic table right here you see a little stairwell like this you see Boron silicon G as antimony tellurium and polenium if you look at this tire well the the elements which forms this terrible is what is called metalloids or some books call it metalloid calls the name semi metal semi metal so it's pretty much the same if you look at the word semi-metals we talk about metalloids so the elements which are on this terrible they are what is called metalloids or semi-metals anything to the left of it or metal when I look at this we are talking about we are looking at this on the screen anything to the left they are all metals anything to the right they are non-metals with only one exception hydrogen is to the left but it is considered a non-metal okay so most of the elements in the periodic tables are metals most of the the one the next one is most uh is non-metals so what is so special about metals and non-metals okay metals usually they are solids again there are always uh exceptions to the rule remember so not necessarily everything is going to be like this most of the metals are solids with an exception here right here this is Mercury number 80 right here Mercury is a metal but it is a liquid it's a viscous liquid in the lab you cannot touch mercury in your hand in the previous days when we have thermometers here remember the thermometer strip will have mercury that's how we note down the temperature uh not anymore they have specialized thermometers where they are going by the sensors and we you don't have a mercury thermometers but in the olden days they used heavy okay so Mercury is a metal but it is a liquid and it's very important most but most of them are solids so usually solids metals are solids they are very shiny in appearance they look very shiny shiny and then what is there is like Metals basically they conduct electricity very important to understand the metals do conduct electricity okay so whatever you send off Metals it's quite the opposite of non-metals non-metals they are usually liquids on gases okay non-metals are liquids and gases they are very dull in appearance and they do not conduct electricity it's quite the opposite of metals again in if I look at the non-metals right here you have iodine right here iodine is a non-metal but iodine is basically a solid remember I told you most of the metals are solid with an exception of Mercury the same way most of the non-metals are either what is called liquids or gases but uh iodine is a solid okay so this is a very general classification so metals are on the left side of the periodic table non-metals are on the right side of the periodic table right here and it is separated by what is called Ester well we call them semi-metals or metalloids okay so if you are asked to find a few names and give me a few symbols and names for Metals give me a few names for um non-metals with a symbol okay so that's basically how we do this so this is a very general classification so let us look into the few slides here coming at the following slides there it's going to say the same here metals are solid right they are good conductors of electricity so they have given you a few examples here okay Metals readily combined with non-metals to form compound that's we are going to see later okay Metals both metals and non-metals they do combine and not necessarily Metals alone but metals and non-metals will combine when a metal combines with a non-metal we call it an ionic compound I'm just saying this here we are going to visit them later on ionic componential compounds and all comes in in much detail in a later chapter let's see where do we get compounds elements uh nomenclature of inorganic so it comes in chapter six so you don't have to worry about it right now all right and let's see what what other thing it says non-metals they are not shiny okay and they are poor conductors of heat and electricity that's basically about non-metals the metalloids have properties between metals and nonmetals in some properties they show like a metal they show some in something they they show like a non-metal okay and one of the thing here is as I go along I'm going to give you a few exercise for you to try here and let's say for example what is the symbol for silver here okay now if you look at this each one of them you might be tempted to pick up s i which is wrong SI silicon is this silver AG this is for gold auram Au is gold and this one is strontium so the correct answer for silver is a g so these are some of the exercise given to use as part of the class notes so I would encourage you to go ahead and do them okay uh here we go it's given answer is silver right there the same thing here which of the following elements are metal I'm going to leave this to you and then look at all these examples here and this is the answer I believe because sodium molybdenum chlorine is a non-metal it is on the right side sulfur is a non-metal magnesium is a metal that's why you see it here PT is platinum you see them Krypton is a non-metal iodine is a non-metal copper is a non-metal copper is a metal okay so as you can see there here uh you can you are looking at uh like uh the choices given and I have given the answer also here okay but uh without looking at the answer I would encourage you to go and find where these elements are that's a good exercise for you to start with okay so that's about uh the general classification let's see what else we have here natural states of the elements okay so this is basically we looked at the most of the metals are solid and most of the non-metals are liquids or gases okay so here it gives you something here error is composed mainly of hydrogen and oxygen homogeneous mixture of diatomic molecules okay this is hydrogen this is oxygen air is basically it's a combination of both okay so that's why we call them a homogeneous mixtures okay and diatomic I will come to diatomic molecules a little later remember I told you the elements are classified into two groups right one of them is a general classification which we call it metals non-metals and semimeters there is also another way of classifying elements in a periodic table I have to come back to this slide right here so this is what is called representative elements okay and it is very important to know them by name okay especially these are main groups like one two you see that group one two in return and then instead of 13 think of this as three three four five six seven eight so like I said one two this one is three four five six seven eight these groups are what is called main group elements the central part we call it a transition metals okay and then for the majority of our class time we are going to spend time on main group elements the transition metals yes we will also look at them a few examples so most of them we will be spending time on this main group elements okay so these are called so um a periodic table is split into what is called representative elements uh Group 1 2 and then remember 3 4 5 6 doesn't have any specific name but in particular there are four of them they have a specific name I want you to know them okay um the first group right here it's called alkali metals alkali metals are extremely reactive okay they react very very well quickly and then not only that even any of these alkali metals what are the metals I have here if I look at the periodic table here lithium sodium potassium so if I look at this one right here these are alkali metals the first group Alkali metal is very reactive with other if I take any of these elements put it in water you will use you will hear a huge like explosive nose they they react very violently with water and not only that they even you don't even have to do anything if I take potassium and leave it on a table a small piece of potassium what happens is it will catch fire very like within a short time so usually these metals are kept in a kerosene or a natural gas they won't leave it just like that they are all solid they won't leave it open like that usually they put it in a liquid so that way it doesn't have any contact with the oxygen all right so the first so this is the whole periodic table I am going to give you the group wise classification or remember I told you the general classification is metals non-metals and semi-metals there is also another way of classifying uh elements in a periodic table based on the main groups here the first one we said Alkali metal the second one is what is called alkaline arithmetals the second groups are all alkaline metals again I'm going to go back to these these one beryllium magnesium calcium strontium barium red radon all those things they are all what is called alkaline alkaline earth metals this is alkali metals this is an alkaline earth metals with an exception alkaline with the exception of hydrogen all right the last two groups also have a specific name the last but the one this one right here the seventh group these are called halogens and the last group the eighth group is what is called noble gases people call it noble gases they also call it inert gases i n e r t inert gases as much as you see the alkali metals are extremely reactive the noble gases they don't react well at all they are very very unreactive do their do they take part in a chemical reaction at all yes they do but under extreme conditions these guys they naturally react so faster okay typically many reactions if you do a metal with a non-metal you take Alkali metal they react with the halogens something like sodium chloride sodium and chlorine here so you look at what are the halogens here halogens are right there this one fluorine chlorine bromine iodine see these are all what is called halogens and what do we call this one noble gases or inert gases so if I give you five elements Choice maybe we may look at an example later on you will look at it something like of the following which is a noble gas of the following which is a halogen so it's very easy for you to answer them okay so these are the four groups this is called Alkali metal this is an alkaline earth metals and the last but one it is called a halogen and then this is called a noble gas what do we call this transition elements okay transition elements are further divided into two groups actinides and the lanthanides for your class you really don't have to know that okay transition metals okay and then you have a main group elements here and what are these called majority of the elements are metals and followed by the number of non-metals and semi metals are very little okay so these are the two classification a general classification of periodic table we say metals non-metals and uh did we see that here somewhere metals non-metals and uh metals non-metals and semi metals the other one is basically what is called um main group elements that are in particular you need to know four of them one of them is alkali metal the first group this one right here this is an alkaline earth metal and this is halogens and noble gases okay so that's basically how uh elements are arranged in a periodic table remember if I look at this one the elements are arranged in such a way when you go from left to right these number will increase you see this one two and then it goes to the next one three four five six seven eight nine ten you come back here 11 12. so these are the numbers on the top we call it as atomic number so basically elements are arranged in a periodic table from left to right and as I go from left to right the atomic number increases OK very important to understand all right and let's see Metals we talked about non-metals we talked about metalloids all right we were looking at this exercise and yeah we also I went through this briefly here and natural states of elements okay so elements tend to be usually reactive and combined with other elements that's how you form compounds okay and add like I said um what is called you see two of them here right two elements combined here if you have two two two atoms combining remember what did I say about elements the smallest part of an element is an atom and most of the elements they can exist as one unit one atom but there are seven elements in the periodic table they are always twins like two of them combine together they don't exist as one atom there are two of them now it's easy to uh given here right here they have given this see these are the Seven Elements hydrogen nitrogen oxygen fluorine chlorine bromine iodine so they all come as two in a pair this is called diatomic molecules dye means two now if you if you look at this list it may be very hard for you to remember I'm going to show you the periodic table so that is easy to remember that way this is the periodic table okay look at this one this is hydrogen number one the first one is a diatomic molecule then after you come here nitrogen this is nitrogen oxygen fluorine go three steps here nitrogen oxygen fluorine you come down three steps chlorine bromine iodine okay so these six elements nitrogen oxygen fluorine chlorine bromine and iodine combined with hydrogen they all come as two units twins that's how it is so in two atoms are combined we call them call them a diatomic uh um element okay diatomic element so they are these Seven Elements remember easy to remember with the periodic table and that's what is being listed here uh we have seen somewhere here right yeah hydrogen nitrogen oxygen so hydrogen is on the left most on the top you start with nitrogen go move two steps to the right oxygen and fluorine and after fluorine you go down three steps chlorine bromine iodine so these seven elements are called as diatomic molecules okay and diatomic say for example in water remember water has two hydrogen and one oxygen right so this is now a kampa now two hydrogens and one oxygen combining now you might be saying just now you said oxygen exists as two how come it is only one remember when oxygen is by itself it is two units together but in a compound it doesn't matter you can have asthma like say for example I have to for water it is two hydrogens and one oxygen there is also an element given NH3 you have there one nitrogen and three hydrogens it's called ammonia okay so in a compound that rule doesn't exist but if the element by itself all the elements in the periodic table they exist as one unit except uh the exception being uh the seven of them right but in a compound it doesn't matter they can exist in uh like uh any number of atoms they have to combine in order to form a compound okay compounds and form this is how see basically water molecule how do you make the water molecule you take a hydrogen and oxygen molecule and hydrogen molecule remember two oxygen two hydrogen and then they are combined in order to form a compound now the next one is uh like you have compounds okay compounds how do you make compounds you make compounds by combining elements say for example if I have to make water I have to combine hydrogen and oxygen if I have to make a carbon dioxide CO2 it is one carbon and two oxygens okay and if I want to make sodium chloride I combine sodium and chlorine so basically a compound is made by combining elements when I say combining elements I mean the atoms of the elements combine in a chemical reaction okay now the compounds are of two types here they don't have to mention it here because we are going to look at a chapter on compounds and naming but here it is just popped up and you can just know it right now molecular and ionic compounds so uh I'm going to revisit again this one in a later chapter but let me give you basically compounds mean you have atoms of different elements combining so what is the difference between a molecular compound and a ionic compound okay uh here don't pay attention these molecular compounds are held by covalent bonds and all it might be you might be wondering what do you mean by covalent bond we have to look at the electrons in much more detail before we can do that so for now ignore this basically compounds are of two type two types okay one is molecular another is ionic so how do I know a difference between molecular and ionic I'm going to give you a simple definition now and later on we are going to visit them in much more detail if you have a metal and a non-metal if you are combine metal and a non-metal we call them ionic compounds okay let's say for example sodium chloride this is an ionic compound sodium is a metal chlorine is a non-metal all right so if you have a metal with a non-metal we call them ionic compounds if you don't have the metal if you are combining non-metals if I combine two non-metals or if I combine a semi metal with a non-metal remember there are three types of uh class like elements are classified into metals non-metals and semi Metals we saw that in other words metalloids so if I have a metal and a non-metal I call them ionic compounds if I don't see the metal if I see only non-metals or a combination of a non-metal and a semi metal semi metal I mean metalloids then we call the molecular compounds so very very important to understand so here water is a molecular compound why because hydrogen and oxygen both are non-metals sodium chloride is an ionic compound why because sodium is metal chlorine is a non-metal okay so very important to know that again these are basically the definitions of molecules if you combine two atoms okay molecules basically are two or more atoms combined together that's what the definition of a molecule now if two atoms come from the same element we call them diatomic element if two elements two atoms coming from different elements we call them diatomic molecule very important to understand say for example oxygen we just now saw diatomic like O2 there are two atoms are arranged two atoms are combined we call them diatomic element if I have say for example C and O one atom of carbon one atom of oxygen I call them diatomic molecule because basically molecules form compounds now as you can look at this one this chapter basically given giving you bits and pieces of information they were sprayed different terms here and this will it will have more meaning later on when we look at them okay what do you mean by ions if you write a symbol with a charge it is called ions okay let's say for example if I say n a and na is the symbol for sodium if I say n a plus then I call it an ion okay now what is the difference between sodium and sodium plus we will look into that in the next chapter I believe when we talk about uh subatomic particles basically ions means I want you to understand what do you mean by ion ion is you and you write any symbol with a charge we call it ions what are the charges I can write either positive or negative if I have a positive charge I call them cation right here so pay attention again it is all given in red here if I have a negative charged symbol I call it an anion so cations are positively charged anions are negatively charged okay so that's what ions are let's see what else is given here compounds okay so here they have given some example of compound this is H2O H2O2 basically what they are saying here it is two hydrogen atoms and one oxygen atom here I have two hydrogen atom and one two oxygen atoms this is what is called hydrogen peroxide H2O2 okay and when you write a formula for a compound remember I can write it in like basically uh in an English sentence but then I should be able to do this here so let's see here one molecule contains two hydrogen atom one sulfur atoms and one oxygen atom so you have to write it like h uh this is like Overkill you don't have to look at it like this you have two hydrogen atoms so you write hydrogen with a suffix two I have one sulfur you don't have to write one in chemistry it is understood okay so this is one sulfur atom I have four oxygen atom o four so this is a when a English sentence is given this is how exactly how you write the formula for a compound formulas are basically a very uh convenient way of doing this because uh someone may not understand English but if you if you go to some other part of the world if you write this symbol they know what you are talking about if you know chemistry right so it doesn't the symbols doesn't have any language barrier basically it you can find out oh this is h2so4 okay now that's RTC being explained if this one is the symbol this is the number of atoms of that symbol sulfur we don't write one remember don't write one in chemistry we we can do that here four oxygen atoms okay that's Tau h2so4 the example we just saw and in this case what you do is like here you have a calcium atom here you have a group of atoms so sometimes we we take a group of atoms and combine them as uh together okay later on we are going to say what is called polyatomic ions but here what it means is is you have nitrogen and oxygen three oxygen this is called the nitrate okay this nitrate I have two units think of them you are putting two different things apples and oranges two apples and orange put it in a box and if I have two boxes of that what does it mean in a single box if you have two oranges and one apple in two boxes how many I will have four oranges and two apples right something like this thing carpet like this you are grouping some atoms together here and then this group think of it as a box I have two of this here now what happens is when when a symbol is given you should know how many atoms are present here okay now calcium I don't see anything here so calcium is one atom right nitrogen also I don't see anything here one but there is a two there so you multiply that 1 times 2 is 2 so I have calcium one atom 2 nitrogen okay which is one plus two is three and oxygen 3 times 2 is what six so if I look if someone asks you how many total atoms are there I have six oxygens two nitrogens and one oxy one calcium so totally I have nine atoms in this unit right there okay so it is very important to know the number of atoms here how many each element is present in k3po4 okay so it's pretty straightforward it is given here three potassium one pass for us and one four oxygens so totally how many elements how many atoms I have now you got to pay attention to the question if I give you this formula I ask hey how many elements are there three of them what are they potassium phosphorus and oxygen if I ask you how many atoms are present in this there is three here one year four here so three plus one is four plus four is eight atoms are there similarly if I ask you here how many elements are there magnesium oxygen and hydrogen three elements are there how many total atoms I have remember there is a 2 there that means I have two oxygen two hydrogens that makes it two plus two is four 4 and I have magnesium there are totally Phi atoms so that's how it has been split here right here okay uh this is like giving the formula and then you have to read it out uh if this is what is called sodium chloride if you do not know at this point it's okay we are going to visit the nomenclature this is so sodium chloride this is magnesium oxide and this is barium nitrate okay and basically how many elements are here two elements sodium and chlorine how many elements are here two elements magnesium and oxygen here how many elements I have barium nitrogen and oxygen supposing if I ask you how many atoms are present in this case I have two one plus one is two here also two what about here I have two nitrogens and six oxygens right two plus six is eight and I have one barium so totally nine atoms are there compensation is basically what it does is if you have two different elements again percent pump position is something we are going to visit later uh if you have oxygen you might be wondering how did you get this one for this we have to find the formula mass and all that's why when you look at a few chapters here sometimes they throw a slide right there but then it may not convey the meaning correctly unless we visit a proper concept so here water will have 11.2 percent and 88.8 so if I have water that's the same percentage hydrogen will always be present in 11.2 percent oxygen will be about 88.8 percent how do we with the calculation we will look at it in a later chapter okay okay again these are some of the things it's in the wrong place we have already seen that in a scientific method so in a scientific method a law and Theory we visit then again it pops up here this has uh like we already discussed in chapter one scientific method okay a law is basically will take the past observation predict the new one a theory is basically a model which explains how things happen and that I think basically what concludes this chapter right here see again learning objectives we have visited all this so we saw what are the uh how elements are distributed how to name them symbols most important thing to remember in one word elements may be in one letter or two letter if it is two letter the first one should be uppercase the second one should be a smaller case and then periodic table where elements are arranged immediately you should know periodic table what are the things I should remember it has two classifications General classifications metals non-metals and semi metal or metalloids I'm sorry I keep using the word semimetal see this is the book where it says metalloids they are the same and then there is also group voice classification Alkali metal alkaline and metal halogens and noble gases I want you to know all those and diatomic elements we saw that there are seven elements in the periodic table which is going to have uh what should I say um they are existing uh two two units together they are called you can think of them as twins there are seven elements hydrogen nitrogen oxygen fluorine and after fluorine it'll be chlorine chlorine Boron and iodine Seven Elements we talked about compounds compounds are made from elements what is the difference between molecular I'm just reviewing that's why I just left the slide also at the end ah what's the difference between molecular and ionic compounds in an ionic compound I will have metals and non-metals in molecular compounds I won't see the metals it's only non-metals or semi-metals and non-metals writing formulas when when I write the formulas remember I write the atom symbol first if that atom has more than one atom I write it as a suffix okay composition of compounds like uh I said the compounds will have something a particular percent uh we will look at that composition uh like how do we get those percentages in a later chapter I hope this will cover chapter 3 and you might probably look at some practice problems which will be made available to you and then please do stay on the schedule there is a schedule posted in modules class schedule and I tried to stick by that schedule so follow them very very closely and that's it for chapter three and then like I said in a later chapter if I need more explanation on the board I can basically write them down right now this one doesn't need a whole lot of working out on the board so that's why I did it as a PowerPoint slide this is a PowerPoint slide available for you in canvas all right um before I go off let me say that making sure that you stay on Pace with the class and whenever the work is given try to finish them do not postpone okay all the best you all have a great day and I will talk to you guys soon okay bye