 Okay, so let's try this again. Aluminum 28, remember I just came up with that number out of my head, okay? So don't get too far down on the mass number, okay? So the following symbol gives the atomic number, mass number, number of protons, number of neutrons, number of electrons, number of valence electrons, and the number of inner electrons, okay? So this particular atom is aluminum 28, okay? So the atomic number, all you gotta do is look up at the periodic table, it'll tell you the atomic number, okay? Aluminum always has the same atomic number as 13, okay? The mass number is given to you in the problem, okay? So you have to be given the mass number to be able to do this one, okay? Or you can be given the number of neutrons alternatively. But anyways, in this problem, the mass number is 28. So the number of protons, like we said before, is always the same as the atomic number. So it's 13. In fact, to be an aluminum atom, you have to have 13 protons. Number of neutrons is going to be the mass number minus the atomic number or the number of protons. So in this case, it's going to be 15. Because 15 plus 13 equals 28. The number of electrons, since there's no charge given here, is going to be the exact same as the number of protons, okay? So it's going to be 13. The number of valence electrons is going to be 1, 2, 3. We count it like that. Or we can look up here at 13 and take off the 1, okay? Valence electrons is 3. The number of inner electrons are every other electron. That's not a valence electron. So all we've got to do is take 13, subtract 3 from it. We get 10. Okay? Does everybody get it now? Okay, cool.