 Okay. Let's try a problem like this. How many protons, electrons, and neutrons are in each one of these ions? So, if you remember this sort of symbolism where you've got the atomic number here, the mass number here, the elemental symbol here, and the charge of the particle here, and remember only ions have charges that are shown. And so, a lot of times you won't be given this information down here because it's redundant information like we've talked about, of course, with the elemental symbol and the atomic number. It doesn't overchange. But anyways, because the number of protons defines what element you are. Anyways, the number of protons is the atomic number, so just write that one down pretty easily, 19, 16, and 12. So, the electrons don't account for any of the mass of the atom as far as the mass number is concerned. So, what we do is we say the number of neutrons is the mass number minus the atomic number. And in this case, it's going to be 39 minus 19, which is 20. 32 minus 16 is 16. And 24 minus 12 is 12. The mass number is an interesting way to define it because you actually define the actual nuclear particle when we start talking about nuclear chemistry or whatever as like potassium 39. So, you are going to define different isotopes. We've talked about isotopes already in the last chapter. So, if you recall, potassium 39 means that it's got the mass number 39. So, there could be different isotopes that have different numbers of neutrons of these particular atoms. But anyways, so the number of electrons would be the same number of protons if the atom was neutral, but these are not. So, in this case, remember, electrons are negatively charged. So, in this case, it's lost an electron because we've got a positive one. So, it's 18. And this case, since it's a negative 2, it's gained 2 electrons, so it's also... Has lost 2 electrons. Ask configuration. Or should...anyways, if you've got a main group. Okay, so hopefully that ends. We'll do the other part of the question separately.