in this lesson we're going to talk about how to determine the charge of an element when it becomes an ion so the first thing you need to be familiar with is the monoatomic ions based on a periodic table so if you go to Google images and if you download a periodic table you'll see these elements on the left you have hydrogen after that is lithium sodium potassium rubidium as a Pure Element these elements have a neutral charge but when they become an ion they will acquire a positive charge so this is the alkali metals now hydrogen is not considered a metal but lithium sodium potassium rubidium those are metals so group run group 1A represents the alkali metals so for instance sodium has 11 electrons but only one electron in its outermost shell so it only has one valence electron when sodium reacts and gives up that valence electron it becomes an ion so the number of valence electrons that an atom has can give you a good idea of what kind of charge it's going to have when it becomes an ion so elements that typically have one valence electron will usually form ions with a plus one charge now in group two we have the alkaline earth metals so like elements like beryllium magnesium calcium strontium these elements are in group two and they have two valence electrons so because they have two valence electrons to give up as an ion they will typically form a two plus charge so calcium which has two valence electrons when it reacts it will typically give up those two electrons forming the calcium two plus ion so metals they typically form positively charged ions whereas non-metals they typically form negatively charged ions now in the middle we have the transition metals which we could talk about that later in this video but to the right we have elements like boron aluminum gallium indium phallium so that's that's the group 3A elements also known as group 13. group 14 or group 4A we have carbon silicon germanium tin and lead now this group they have three valence electrons so you might be thinking that they will form a three plus charge which in fact they do but some of these elements also form a plus one charge now I don't know for you the viewer if you've learned electron configuration but if you have these elements here they have S electrons these elements here they have P electrons so for indium actually let's use aluminum aluminum when you write the electron configuration it's 1s2 2s2 P6 3s2 3p1 notice that it has three valence electrons when aluminum gives up those three valence electrons it will have a three plus charge now the elements below that like gallium and indium and thalium instead of giving up all three electrons sometimes they could just give up one electron and so they can have a plus one charge so understanding electron configuration will help you to get a better understanding of what type of charges certain ions or certain elements form when they become ions so gallium indium thalium they will typically form a plus one or a plus to recharge dependent on the reaction conditions now here we have group 4A Elements which has four valence electrons and they can form four plus charge but like these elements some of them can have a two plus as well so if you look at the electron configuration of silicon it's 1s2 2s2 P6 3s2 3p2 now if silicon gives up all four of its valence electrons it's going to have the four plus charge if it gives up only two it's going to have the two plus charge so silicon germanium tin and lead when you research them you'll find that they can have the the plus two oxidation state or the plus four oxidation state now group 5A elements like nitrogen phosphorus arsenic these are non-metals arsenic may be considered a metalloid it's kind of close to that region but nitrogen and phosphorus or non-metals remember we said that metals like to give up electrons to form positively charged ions known as cations not Metals which is typically in this side of the periodic table they like to acquire electrons and form negatively charged ions called anions now nitrogen has five valence electrons and it wants to acquire electrons to have a field octet so it wants to gained three electrons to satisfy its occset requirements once it gains those three electrons it's going to have a three minus charge so group 5A elements they will typically form a three minus charge now group 6A elements they have six valence electrons this is like oxygen sulfur selenium and they only need two more to get to eight once they acquire those two electrons they will have a charge of two minus and then you have the group 7A elements like fluorine chlorine bromine iodine these are the halogens group 6A they're the calcagens now the halogens they have seven valence electrons they only need one more to get to eight so they will generate a negative one charge once they get that one electron to have eight electrons in their outermost energy level so that's how you could determine the charge of an element when it becomes an ion using the periodic table it has to do with the number of valence electrons when metals give up the advanced electrons they will acquire a positive charge and that positive charge is determined by how many valence electrons that metal gives up the nonmetals when they acquire electrons the number of electrons that they acquire will determine the charge that they're going to have so here's a formula that will help you to calculate ion charge the ion charge is the difference between the number of protons that an atom has and the number of electrons so let's use aluminum as an example aluminum if you look up in a periodic table it has a mass number of 27 and an atomic number of 13. now an atom has an equal number of protons and electrons so atoms are electrically neutral ions the reason why they have a charge is because the number of protons and electrons are different and another thing you need to know is that the atomic number of an element is equal to the number of protons so aluminum will always have 13 protons if that number is different it's no longer aluminum as an atom aluminum will have 13 electrons and so its ion charge will be zero now in order to form this three plus charge aluminum has to give up three electrons when it does that it will have 10 electrons and so 13 protons minus 10 electrons you get a charge of plus three or three plus in the case of oxygen oxygen has a mass number of 16 an atomic number of eight so as an atom oxygen has eight protons eight electrons so it's ion charge is zero now when oxygen gains two more electrons to satisfy its octet requirement it will have 10 electrons and so at that point its charge will be negative two so that's the formula for calculating ion charge it's simply the difference between the number of protons and electrons that the ion has now sometimes you might be given the formula of an ionic compound let's say like this copper to chloride when you see this Roman numeral it tells you the oxidation state of the metal so it tells you that you're dealing with the copper two plus ion because when you're dealing with transition bottles many of the transition metals have multiple oxidation States so as an ion they can have different charges so even like some of the non-transition the non-transition metals like lead lead has two oxidation States we talked about it already two plus and four plus so if you see a compound that says lead to oxide the Roman numeral two tells you you're dealing with pb2 Plus if you see a compound that says lead four sulfide well in this case lead has a four plus charge so make sure you understand that difference but with that being said let's go over some of the common charges of the common transition metals that you'll deal with in a typical chemistry course so the most two common oxidation States for copper are these two the copper plus charge and the copper two plus ion now the copper two plus ion is more common than the copper plus one ion so if you don't have a compound with a Roman numeral and if you have to guess chances are it's more likely going to be copper two plus than copper plus one but both of these can occur now for Iron Metal there's two common oxidation States two and three so those are the two most common ions you'll see with iron metal fe2 plus is more stable than fe3 plus so iron is usually most likely to be in this form now Cobalt has two common oxidation States it has others too but these are the most common the two plus and the three plus ion the two plus ion is more stable so that's going to be more common zinc nickel cadmium most of the time and they will have the two plus oxidation stain now this is not always the case but in a typical General chemistry course more than 90 of the time those will be the charges of those ions for chromium it's usually in one of these two forms two plus or three plus nine percent of the time silver is in the plus one oxidation state I've also seen a plus three oxidation state for other compounds but more than ninety percent of the time will be AG plus one gold I've seen plus one and plus three for this so if you want to commit that to memory those are some charges that those elements will form as an ion now for the polyatomic ions for the most part you need to Commit This to Memory what I'm going to do is I'm going to post some videos in the description section below this video one of which will be the polyatomic ions that you need to know so feel free to watch those videos if you want to memorize the charges of these ions so sulfide which we talked about earlier this is what is known as a monoatomic ion mono means one poly means many sulfite so32 minus that's a polyatomic ion because this ion is composed of many atoms one sulfur atom and three oxygen atoms sulfate that's also a polyatomic ion notice that the sulfur ions they typically have a two minus charge the monotomic ion phosphide has a three minus charge phosphite and phosphate also have a three minus charge now this works for the halogens as well so chloride bromide iodide they follow this trend chloride has a negative one charge and the same is true for hypochlorite chlorite chlorate and perchlorate they all have the same charge so at least that'll help you if you're trying to memorize this now not all elements follow this trend nitride has a three minus charge but nitrite and nitrate has a negative one charge so for those elements it's different and for other polyatomic elements you just have to commit them to Memory so like cyanide ammonium carbonate acetate most of these you have to commit to memory now there's something else that can help you to determine the charge of an ion particularly if hydrogen is evolved so for instance oxide has a negative two charge and let's say we want to determine the charge on hydroxide whenever you add a hydrogen to a negatively charged ion and you combine them together to form a new ion these ions they attract to each other because they have opposite charges Opposites Attract like charges repel when you combine these two ions the ion of discharge will be the sum of these two exponents so if you were to add negative two and positive one you're going to get negative one so hydroxide has a minus one charge consider this example phosphate which has a negative three charge if you add a hydrogen ion to it and you get monohydrogen phosphate negative three plus one will give you negative two so this has a negative 2 charge if you add another hydrogen to it the charge is going to decrease it's going to increase by one so negative two plus one this is going to be H2 po4 now and so it's going to be -1 and so forth so for instance let's say if you have this substance by sulfate or hydrogen sulfate actually that's bisulfite or hydrogen sulfide what is the charge on hydrogen sulfide you know that sulfite has a negative two charge hydrogen has a plus one charge so if we combine them together negative two plus one that'll give you a negative one charge now earlier we said that ammonium has a plus one charge so if you were to combine nitride with four hydrogen ions this will give you ammonium so if we were to do the math we have negative 3 and we have four plus one ions so that's negative three plus four that'll give us positive one so ammonium has a plus one charge so that's another way or another technique that you can employ to determine the charge of an ion or even polyatomic ions but for the most part you're going to have to memorize the polyatomic ion list so that's it for this video don't forget to check the links in the description section below for other related chemistry topics and thanks for watching