hello again and welcome to gemistry health.com my name is Dr Kent and this lesson is a continuation of our series on ionic compounds now in our previous lessons we learned how to name monoatomic ions how to name polyatomic ions and then we learn how to take names and turn them into formulas well now we're going to learn how to take formulas and turn them back into names so as a quick little reminder ionic compounds typically have a metal as the cation now they don't have to they could have a polyatomic ion let's say they could have ammonium could be the Caton but 99% of the time most of them have a metal now there's two different types of metals there are fixed charge metals that means the charge of those Metals is always the same those are sometimes called type one Metals then there are variable charged metals or what are called type two and those the charge just like it says can vary so sometimes they're plus two sometimes they're three plus so the fixed ones are easy to pick out those are all of the metals in group one group two and then what I call the Magic Triangle these over here so remember all of these Metals in group one lithium on down here these are all 1 plus so lithium when it makes an ion makes positive sodium positive pottassium positive of Rubidium cesium Etc all of these Metals in group two on down here well these all like to be two positive so brillium two positive magnesium two positive calcium strontium barium so those are all fixed charge now the ones over here in the Triangle these also don't change their charge so remember I told you in that lesson that these three aluminum gallium indium these three like to be three positive these two zinc and cium like to be two positive and this one silver likes to be one positive so there's three that are three positive two that are two positive one that's one positive all of the other metals pretty much so titanium vadium mbum I mean just name one tin bismo um any other one you think of uranium idium whatever any other metal that's not group one not in group two not in the Magic Triangle very likely it's going to have a variable charge so just for a little reminder iron iron sometimes it likes to be Iron 2+ sometimes it likes to be Iron 3+ and as we said in our lesson on monoatomic ions since it can vary we have to name it special so iron 2 plus we call iron 2 with a Roman numeral iron 3+ we call iron 3 with the Roman numeral okay well let's just go through and and see so if the charge has gone a vary on the metal well how do we figure out what it is in a compound well we figure it out by whatever the charge is on the annion so for example let's look at Cobalt three of those and nitrogen two of those so Cobalt if we Peak back over here Cobalt lives right here so yeah Cobalt's not in group one it's not in group two it's not in the Triangle so it will have a variable charge so I know it's going to be Cobalt but something with variable charge I's put parentheses here well this number is determined by whatever the charge is on the anion so let's go back here so here's nitrogen that's the other part so again we learned in that lesson on monoatomic ions that non-metals gain electrons until they get as many as the noble gases over here so all of these in group 17 are one away so they all want to be one negative all of these in group 16 are two away they want to be two negative all the non-metals in group 15 are three away they want to be three negative so nitrogen when it becomes an annion the ending changes to I we call it nitride and it gains three electrons so Cobalt something nitride and again nitride is 3 negative well how many nitrides do we have though well we got two of them so that's a total toal of 2 * 3 a total of 6 negative well we learned in ionic compounds that they always balance out the positives and the negatives so if the total negative is 6 negative well the total positive has to be six positive okay now six positive though doesn't mean it's Cobalt six because there's three Cobalts so the combination of Cobalts they combine to be six positive so 3 * what would be six positive well each one would have to be two positive so 3 * 2 positive will give me a total of six positive so must be Cobalt 2 okay let's just go ahead and work a few examples here hgs so what's HG HG is mercury let's find Mercury it lives right over here okay so it's not in group one it's not in group two it's not in our Magic triangle so that means it does have a variable charge so I know it's Mercury something why figure out the charge based off what the annion is well the annion comes from sulfur so when sulfur becomes an annion we call it sulfide non-metals by themselves just go to ey what would the charge be well it's one two away from argon so it must be 2 negative right so we got a total of two negative on the anion so we must have a total of two positive on the cats there's only one so each Mercury must be two positive Mercury to sulfide great how about this one let's find Fe so Fe is iron where does iron live okay right here so again iron's not in group one it's not in group two it's not an our Magic Triangle so its charge is going to vary so iron something well we figure out the charge whatever that is based off the annion so what's NO3 well as you might recall from our lesson on polyatomic ions that is called nitrate nitrate okay what's the charge on nitrate well nitrate is one negative but we have three of them so three one negatives gives me a total of three negative so the positive total must be three positive in order for it to balance out so there only one iron so it must be iron 3 nitrate mgf2 we find mg okay well mg is in group two so that means it's always two positive so we don't need a Roman numeral because it can only be one thing so again there's no reason to say magnesium Roman numeral two because it can only be two so we just name it magnesium and then we name F how do we name that as an anion well it comes from Florine and when non-metals become annion they change to I so magnesium fluoride and make sure when you spell it you put the U before the O It's fluoride not OU fluide fluide SN parentheses CN parentheses 4 so SN that's called 10 let's find 10 oh number 50 okay well it's not in group one it's not in group two it's not in our Magic Triangle so it will need a Roman numeral we figure it out based off whatever this is what's CN called well CN is one of the polyomics you just have to learn it's called Cyanide and it has a one negative charge well we have four cyanides that's a total of four negative the positives and the negatives have to balance out so if that's four negative the 10 must add up to be four positive there's only one of them so it must be 104 so 104 cyanide number five cu2o so CU is copper so will copper need a Roman numeral well we got to see where it is copper is right here so it's definitely not in group one it's definitely not in group two and it's not what I like to call the magic triangle so it's not a fixed charge so yes it will need a Roman numeral well we got to figure it out based off whatever the charge on this is so oxygen when it becomes a annion the ending just changes to iide so oxide what's the charge on oxide well oxygen lives two away so it would want to gain two electrons to become at the noble gases so it's 2 negative well we only have one oxygen that's a total of two negative which means the the total over here has to be two positive but notice there's not just one copper now there's two coppers so these two coppers combine to give me two positive so what would each copper have to be well two * one positive would give me two positives so each copper must only be one so copper one oxide number six zns SO2 so ZN that's zinc let's find zinc lives right here so it's not in group one it's not in group two oh but it is in our Magic Triangle so that means its charge doesn't vary remember these two are always too positive so I don't need a Roman numeral but I do need to figure out what this is so this is a polyatomic sulfur with some oxygens so we figure out what this is by knowing what the eight is the one that ends in eight so what's sulfate okay well sulfate is s so42 Nega so what do we have here well we have SO2 so this has two less oxygen so we're down here at s SO2 but still two negative cuz look we lost two oxygens so sulfate is so4 what would SO2 be well we change 8 to I and then we add hypo so it would be hypo sulfite zinc hyposulfite great number seven CR what's CR well CR lives right here and that is chromium so will chromium need a Roman numeral it sure will it's not in group one it's not in group two it's not in our Magic triangle so it charge is going to vary so we got to give it a Roman numeral we base it off of whatever this is so this is a polyatomic in other words what is the eight for phosphorus so what is phosphate well let's see phosphate hopefully you know is P4 3 negative what do we have we have P3 oh well that's one less oxygen right so instead of phosphate we would call that fosite but the charges don't change when you add or remove oxygen so it's still three negative okay so phosphite has a three negative charge how many do we have we got two phosphites that's a total of six negative so our catons must add up to be a total of six positive so what's chromium have to be there's only one of them so it must be chromium 6 well hope you enjoyed this lesson on naming ionic compounds for many more practice problems be sure and click on the link and we will see you next time on getchemistryhelp tocom thank you