 Okay, let's start the day off with some isotope questions. So the first one, the atomic symbol for two isotopes of chlorine are shown below. Calculate the number of protons, neutrons, and electrons for each. So what do we have here? We've got the two major isotopes of chlorine, chlorine 35 and chlorine 37. And they want you, of course, to calculate the protons, neutrons, and electrons of each of these things. So they're atoms, not ions, so you know that the number of protons and neutrons are the same. And that's going to be the same as the atomic number. Remember the atomic number is written on that as a subscript to the left of the atomic symbol. So that shows the number of protons. So in chlorine, to be a chlorine atom, you have to have 17 protons. And to be a neutral chlorine atom, that means you have to have 17. Throughout the neutrons, it's just the mass number, which is up here, minus number, which is 37 minus 17 is 20, and 35 minus 17, of course. So that's how you calculate the number of protons, neutrons, and electrons. And we've done that before for individual atoms. But I guess now we're looking at things that are isotopes against each other. And what we see is the only difference between these isotopes are mass numbers are different because the number of neutrons that they have is different.