oh hello this is another lecture topic video for Isotopes and ions so remember when we're talking about an atom all right it's made up of three particles remember we have protons we have neutrons those are in our nucleus okay electrons okay so let's remember that our protons carry plus one Cherry zero charge and our electrons carry a minus one charge okay and so generally when we're talking about a neutral atom all right the number of protons equals the number of electrons okay the other really important thing about the number of protons is it dictates the atomic number of a given element okay so again the atomic number equals the number of protons in the nucleus of an atom of a given element right so that's essentially how we identify the different elements that we find on the periodic table and so if we go back here all right you'll see for example carbon all right it's got an atomic number of six that tells us that there are six protons within the nucleus of that atom of carbon all right and so then we can introduce this concept of mass number well the mass number is a little bit different it is the number of the total protons and the neutrons in the atomic nucleus of an atom so if we're thinking about how to represent these things as symbols so if we come down here uh to the symbols what we can see is that we would give the abbreviation or the symbol for the element okay in this case it's X our atomic number again the atomic number for any given element stays the same that's what gives it the I that's what gives that element its identity all right we put that in a subscript to the lower left hand corner okay so right here and this mass number which again is the number of protons plus the number of neutrons would be subscripted in the upper left hand corner right and so now how does this play into this definition of an isotope well an isotope is an atom of the same element okay in other words they have the same number of protons okay again the protons what gives a particular element its identity but they have different numbers of neutrons okay so again they have identical atomic number but they have different Mass numbers okay and again why is that well because the thing that's different between two isotopes of an element is the number of neutrons all right so that goes into determining the mass number so let's take an example of hydrogen there are three stable isotopes of hydrogen so there's protium deuterium and tritium so if we're looking at protium okay or hydrogen as we like to think about it it has a single proton so if we're writing out the symbol for protium or hydrogen we would write hydrogen one okay and so by writing this it tells us that we're dealing with hydrogen again this atomic number gives us the identity of the element again one is hydrogen you can go back to your periodic table start to get comfortable with that all right and then what do we have we only have one proton there are no neutrons so the mass number in this case because mass number is the number of protons plus the number of neutrons well there are no neutrons in this case so it is also a one so that tells us that this element of hydrogen has one proton no neutrons and one electron because there's no charge on it all right so and again if we have no charge our uh protons and our electrons have to be equal to one another the number of those two things all right so let's move to deuterium okay well in this case now we have a single proton and a single Neutron again because we have a single proton that tells us again we're dealing with hydrogen so we can write our element symbol and we can write the atomic number subscripted to the lower left hand corner and now we have one Neutron again our mass number in this case is the number of protons plus the number of neutrons so in this case it is two now moving to tritium um this is another stable isotope hydrogen in this case one proton and two neutrons right so we write our symbol we would write that we're done with hydrogen so we have a single proton but now we have two neutrons so our mass number again the number of protons plus the number of neutrons and that would be three okay just so we can kind of connect this to Everyday Life uh tritium is actually something that's used in quite a few researchers um science that they do in their Labs mine for example okay so this is a stable isotope of hydrogen that I use uh routinely in my research so how are we going to write these things so when we write these so this is written in terms of their symbols okay so this is the symbols but we can also write these names out and how are we going to write these out we would write them out according to their mass number so for proteum all right this would be hydrogen dash one okay or we can use a symbol to help us with this we can write H1 and for deuterium it would be hydrogen 2 or H2 okay again uh that's for this guy we have one proton and one Neutron and for tritium we would have hydrogen [Music] three four h three okay so again these are all representing okay the mass number all right so that's an isotope now what we'll also find as we proceed uh through the course is that we can make things called ions all right what is an ionic ion is an atom or a group of atoms okay that has some net positive or negative charge okay so it's an atom or a group of atoms with an overall charge and that charge can be positive or negative okay well how do we get these things well what you're going to find is that we're going to start making bonds between things um and and and what we're usually moving around okay is not our protons and our neutrons but it's electrons so we get these things from either gaining electrons or losing electrons all right so what types of ions can we have again they got some special names so if it's a positive ion these are called cations okay so again let's take an example here of neutral sodium okay again neutral sodium suggests that we have um the protons is equal to the number of electrons okay so again this is typically the case if we're talking about a neutral atom of a given element okay well again we have 11 protons again this tells us that we're dealing with sodium so we can go back and take a look and you can see here that sodium has 11 okay for its atomic number so it has 11 protons foreign so we have 11 protons and somewhere outside of the nucleus are surrounding this this um this nucleus are 11 electrons well what happens if we lose one electron okay if we lose one electron we still maintain the same number of protons again this is what tells us that we're dealing with with with sodium okay all sodium have 11 protons all right but what we've done is we've lost one negative charge so what we have is a nucleus with a plus 11 charge and now we only have 10 electrons all right so 10 units of negative charge and so what do we get for our overall charge on the sodium we get a plus one all right and so that's written as sodium plus all right where that plus is superscripted to the right hand side okay so that is a cation well how about an anion an anion again is a special name for a atom or a group of atoms that are carrying a negative charge okay and so let's take an example of chlorine again 17 protons in our nucleus this identifies it as being chlorine and neutral chlorine has 17 protons plus 17 electrons again that's why it's neutral okay so now let's say that this chlorine atom has essentially accepted an extra electron from somewhere well now the number of protons stays the same all right but now we have 18 electrons so what's the overall charge well now we have a plus 17 because of our protons all right and then we have minus 18 unit of charge from our electrons so let's just say protons this is coming from our electrons and so our overall charge is now a minus one all right so now what we can do is we can write the symbol for this as chlorine and then again we denote the charge on the chlorine whatever the atom is or whatever the group of atoms is to the upper okay right hand side so it would be chlorine minus all right and again this tells us that somewhere or along the line This chlorine has adopted or accepted an extra electron from somewhere in its environment giving it this extra negative charge classifying it as an anion so here's a sample problem the question is how many protons neutrons and electrons are there in uranium to 35. well remember when we're writing this out this 235 is telling us that we're dealing with the mass number and the mass number is equal to the number of protons plus the number of neutrons okay and so we know we're dealing with uranium okay we can go back to the periodic table real quick and look for Uranium uranium is right here okay so it's got an elemental symbol of U and as we can see here has nine an atomic number of 92. all right so remember our atomic number tells us about the number of protons okay so what we can do is we can start to write some information out we know we're dealing with uranium and we know that it has 92 protons that is the atomic number okay well now we know the mass number is 235 okay and we know that we have 92 protons plus the number of neutrons equals to 35. so therefore the number of neutrons is equal to 143. okay and so we can even write this over here in our symbol all right because again our mass number goes to the upper left hand side so now we know the number of protons okay from our atomic number from the periodic table that's 92 we now know from our mass number and the number of protons how many neutrons we have that's 143 and we're dealing with something that is electrically neutral at least that's what we have to assume because the question didn't tell us so remember that the charge is equal to the number of protons minus the number of electrons okay well if the charge is equal to zero in this case and we have 92 protons minus the number of electrons equals zero therefore the number of electrons has to be equal to 92 as well so in this case we have 92 protons 92 electrons giving us a net neutral charge and from our mass number and the number of protons we can determine that we have 143 neutrons remember at this point 92 is a little redundant because we can tell from the periodic top table that um that that is the atomic number and again the atomic number is what identifies it as being uranium so again the question already told us that we're dealing with uranium so really this is a little redundant but for completeness sake I'm just going to leave it in there but we can also write this out okay so we can also write this out as being uranium to 35 which was again given in the question so here's another sample problem which neutral isotope is described by the following information and in this case we have a 54 electrons 79 neutrons so again how do we start this question well it's telling us that it is neutral it's a neutral isotope well if it's neutral is equal to the number of protons minus the number of electrons in this case it's equal to zero so if we have 54 electrons we can easily solve for the number of protons that would be 54. okay so we're dealing with an element that has an atomic mass or atomic number excuse me of 54. so remember this is the number of protons and the number of protons identifies what the element is so let's go back and look at the periodic table and let's find 54. well 54 is Xenon okay so let's go back to our question so we know we're dealing with Xenon 54. again 54 is a little redundant here because uh 54 tells us that Xenon and Xenon by definition tells us that it has an atomic number of 54. so um what can we do to determine this mass number because we're talking about an isotope what's the stable isotope so remember our mass number is equal to the number of protons plus the number of neutrons well now we've already determined that we have 54 protons all right and we were given the number of neutrons so we can plus 79 and what we can do is we can add these two things together to give us a mass number of 133 right so for simplicity's sake if we're talking about representing this in terms of symbols can write 133 okay we don't have to indicate any sort of charge here which would go there all right um because it already tells us it's neutral all right and so this is in fact uh the neutral isotope all right but we can also write this out okay and so again we can write this out as Xenon all right and we can call this 133 because again we identify it by the mass number or as with the hydrogen example we can also write this out in a semi-symbolic way Xenon 133. okay so now are a couple participation questions so the question here is how many protons neutrons and electrons are there in the following isotope well we've given you the mass number okay and in this case we've given you a charge it is a cation carrying a plus two overall charge so again your goal is to figure out how many protons neutrons and electrons we have again knowing that we're dealing with a isotope of magnesium okay isotope of magnesium a second participation question so which isotope contains 27 protons and 32 neutrons so use these this information to tell me which of the Isotopes um that you're dealing with all right if you have any other questions um please reach out I'm happy to try and get your questions answered and if not I hope you have a great rest of your day and I will talk to you soon foreign