Learn about Junior Chemistry, Compounds 2, in this comprehensive video by bannanaiscool.
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Rob Lederer: Okay, let's practice couple of other ones. Aluminum ion has three positive charges. Oxygen ion or oxide ion is a two negative charge. So, what's the formula there? Well, this has to lose three electrons, but this only one is two. If you had two Als losing electrons, you have six electrons lost. Do you understand what I'm saying? Two, three positive charges mean six electrons lost. O2 negative, I'll take two electrons. if I had another one it would take two more, that's four. If I had another one that would be a total of six that it would take three Os for every two Als, works in this case and you get AL2O3, the name is Aluminum Oxide. There are some ions on the periodic table not really on the table, so much as they are on a separate chart and it's called the polyatomic ion chart. Polyatomic, many atoms, and so this is sulphur and oxygen all what we call covalently bonded. they're bonded as a molecule, and then this molecule assumes a charge and it will take two electrons. So, it's an ion, it's an anion, a negative ion. here is your cation, the Fe3 positive. Now, how are these two are going to come together. Just watch. Just like this one here, you need two of these for every three of these. I hope that makes sense. And so, therefore how we are going to be able to write that as a formula. it's really straight forward you know. We need two of the Fes, but we don't write the charge anymore, okay? We are just saying we need two of these Fes and we will just get rid of that charge. How many of these did we need, these So4s? there was a two negative for this entire So4 and so that means then, that we need or require three of the So4s. so, we got So4, but we need three, so we put brackets around it to say we need three of those whole things. So, you see we need three Ss and there is three times four is 12 Os. So, that's how we do chemicals that are polyatomic ion in nature. There are lots of these that we are going to practice with coming up. A little something else that will help you in terms of getting things organized with that polyatomic ionic chart is that not all the polyatomic ions are there and you have to know some of the nomenclature of how to name certain things. For instance, ClO3 negative is generally on the chart and its called chloride. So, chloride is one that's popularly found on a periodic table. This one because, it's one less oxygen with the chlorine, but the same charge, that guy is name is chlorite within an ite instead of an ate. So, ite just means one less oxygen then ate. Now, there are some of that aren't located on the chart generally. One might be ClO4 negative, which is one more than the ate and then there is ClO negative, which is one less than the ite. if you go less than an ite, you got what, here is a prefix for one less, hypo. that hypo just means less like hypodermic below the skin, it's a needle. Right, get it, okay yeah good. So, hypo means one less and so we go hypochloride. that would be one word hypochloride. and that's what that one is called, what's this one called, well, one more would be hyper, hyper just means to have more like when you are hyper active, you are more active hyper active. So, the thing is, this should be called hyperchlorite because it's one more than an ate, but actually its called we got to drop the hy and go per, don't ask me why? I don't know. So, it's just called per for hyper chlorate and you can do that with any ion. you can look on your chart for sulphate, there is a sulphite. there could be a hyposulphite and a persulphate as well as nitrates and things like that. Have some fun with it. Chemistry is all about fun.