 When an atom has unequal numbers of electrons and protons it has a charge and then we call it an ion. In this video we're going to look at how you name these ions, why various ions have the charges that they do, and also look at some more complex ions that are made of several atoms joined together. First of all a bit of vocabulary. If an ion is just a single atom we call it a monatomic ion. This comes with the suffix mono meaning one. And if it's made from more than one atom joined together we call it a polyatomic ion because poly means many. And as you know the key feature of an ion is that it has a charge, it can be either positive or negative. If the ion has a positive charge then we call it a cation. And if it has a negative charge we call it an anion. First let's look at simple monatomic ions. Monatomic means made of one atom so a monatomic ion is simply an atom that has either lost some electrons and become a positively charged cation or it's gained some electrons and become a negatively charged anion. So here's our periodic table and I'm going to shade the elements that usually form positive ions in blue. This corresponds to the metals as well as hydrogen. Hydrogen can also form positive ions. And I'm going to shade those that usually form negative ions in orange. This corresponds to the nonmetals and also hydrogen. It's rare but hydrogen is able to form a negative ion. The white ones that are left over on the right hand side, the noble gases, they rarely form ions at all. I'm going to talk about those later. For our purposes here what you need to know is this. If a monatomic ion is positively charged then its name is the same as the neutral atom. This usually happens with metal atoms so when a sodium atom becomes an ion we simply call it a sodium ion. And you can have tin ions and uranium ions and iron ions. Hydrogen can also form positive ions as we've said and they would just be called hydrogen ions. If instead you have a negatively charged ion and this usually happens with the nonmetal atoms then you change this end of the name to ID, IDE. So the ion made from a nitrogen atom is called a nitride ion. An oxygen becomes oxide, fluorine becomes fluoride, sulfur becomes sulfide, tellurium becomes telluride and so on. Under certain conditions hydrogen can also form those negative ions and in this case it would be called hydride.