this is an introduction to naming ionic compounds with transition metals the transition metals are the elements in this part of the periodic table and when we write the name for an ionic compound that contains transition metals those names usually have Roman numerals in the middle of them so in this video we'll learn how to take the formula for a compound that contains a transition metal and how to write the name for it with Roman numerals and everything so transition metals the transition metals are the elements in this part of the periodic table here and I've written in some of the most common I'm also going to be talking about some of the metals over here which aren't technically transition metals but they act a lot like them these metals are unique because many of them are able to make multiple ions with different charges so iron Fe for example is able to make an fe2+ ion but it's also able to make an fe3+ ion okay this is different from the metals say over here they tend to always make ions with the same charge sodium for example is in this + one column here and so when sodium is an in an ionic compound it always makes an ion with a one plus charge magnesium here is in this 2+ column so when it is in an ionic compound it makes a a 2 plus ion but the transition metals can make a wide variety of different ions with different charges some of them can even make four or five different ions each with a different charge so these different charges on transition metals really come into play when we want to name a compound that contains a transition metal so here we have fe3 and for the F the iron we can't tell right away just by looking at this whether the f Fe is fe2+ or whether it's fe3+ right we have these two different types of ions that Fe can make now we can distinguish between these two ions by using Roman numerals to give them different names so the fe2+ ion we call that iron 2 with the Roman numeral for two in parenthesis the F3 plus ion we call that iron 3 with a Roman numeral for in parenthesis and we'll use these ion names when we want to name the whole compound so if the Fe here turns out to be fe2+ we'll call this compound iron 2 chloride and if this iron is iron 3+ we will call the compound iron 3 chloride so in order to figure out whether we're talking about iron 2 chloride or iron 3 chloride here we we got to do a little bit of math and work backwards to figure out which of these two charges iron has in this particular compound let me show you how to do it so to find the charge of a transition metal we start by focusing on the ion with a charge that we do know that's certain that's not going to change and for this that's going to be cl cl is in this column here on the periodic table so that we know that in an ionic compound CL always makes an ion with a one minus charge Okay so we've got cl1 minus now how much total negative charge do we have here we have three CLS so that's going to be 1 2 3 and since we have three of them the total amount of negative charge is going to be 3 minus now in an ionic compound the negative charge always has to balance out with a positive charge so if we have three minus on this side we've got to have 3+ on this side so what's the charge on iron now well there is one iron ion in this compound which means that all of the positive charge has to be on this one ion which means that its charge is fe3+ okay so one ion of fe3+ gives us three plus of charge which has to be balanced out by the 3 minus over here which is distributed over the 3 CL minuses so that's how we figure out the charge on iron and since this is iron 3+ the name for this compound is going to be iron 3 and then for cl when CL when chlorine becomes a negative ion we call it chloride the ID usually gets added to the name of an element when it becomes a negative ion so chloride is what we call CL 1 minus so iron 3 chloride is the name of this compound we had to work backwards and figure out the charge of iron and then we can call it iron 3 so if you want to get really good in naming compounds with transition metals and using the Roman numerals and all that you've just got to get a lot of practice so I've made another video that's just a whole bunch of practice problems on naming ionic compounds with transition metals but before you check that out I want to talk about a couple of important things the first thing I want to talk about is when we use Roman numerals for naming and when we don't this confuses a lot of students okay so when do we use Roman numerals well we use Roman numerals when we're naming compounds that contain transition metals so here are three compounds that contain transition metals and as as you can see we use these Roman numerals and we use the Roman numerals because copper iron and vadium are transition metals which means that they can make multiple ions with different charges so we kind of need to pin down the specific ion that we're talking about in each one of these compounds right so we put this one here to say we're talking about copper one plus because copper could make other ions we're talking about iron 3+ here we're talking about vadium 4 plus because they could be a variety of different ions now on the other hand we don't use Roman numerals when we're naming compounds that don't contain transition metals that contain for example the metals over here take potassium iodide for example potassium K is in this column it's in the 1 plus column which means that in an ionic compound pottassium always makes an ion with a one plus charge that's the only choice it can only be 1 plus so we don't need to put a Roman numeral in there to specify that it's 1 plus because that's the only choice that it could be calcium nitride over here calcium is in this 2+ column and it can only make an ion with a two plus charge in an ionic compound so again we don't need a Roman numeral to say that because there's only one choice and that's 2 plus now aluminum over here can only make a three plus ion so you don't need to use Roman numerals with aluminum either and I should point out that some of these Metals here that are not technically transition metals still can make ions with different charges so we have to use Roman numerals when we name compounds with tin and lead in them as well but here's a big point if you're naming compounds with ions that can make different charges you always need the Roman numerals but don't put those Roman numerals in if you're naming compounds with metals that can only make one uncharge not only is a waste of time to put those Roman numerals in but it's wrong you just shouldn't put them in there now we have to use this method of working backwards in order to name compounds that contain most transition metals and we also have to use this method to name compounds that contain metals like tin or lead that are able to make more than one type of ion but there are two important exceptions that I need to tell you about and these are silver AG and zinc ZN even though these two elements are transition metals they're only able to make one type of ion so silver AG always makes AG one plus it's always one plus and only 1 plus zinc ZN always makes an ion that is zn2+ now that means that when we name compounds to contain silver or zinc we don't have to use Roman numerals because we're only talking about one type of ion okay so a compound like this agcl you don't have to do any math at all you don't have to use a working backwards approach you just call it silver chloride zncl here super easy we just call that zinc chloride and since these elements always make ions with just one charge we don't have to use the Roman numerals when we're naming them so it would be wrong to call this silver one chloride or zinc two chloride here there's only one possible ion so we don't use the Roman numerals we only use the Roman numerals if we're trying to distinguish between multiple types of ions with different charges so that's an introduction to how we name compounds that have transition metals in them in the next video we'll do a whole bunch of practice problems so you can really get the hang of it this is one of the things that you just get better and better at with more practice so check out that video you'll get super good at it really fast