 OK, so let's do another one of these problems. Calculate the number of protons, neutrons, and electrons in iron 55. So iron 55, you're going to have to remember if it's not written for you, like I wrote it up here for you, how to write it. So iron's atomic symbol doesn't look isn't I or IR or anything, it's FE. Ferris is what it comes from. But anyways, remember 55, the number 55 refers to the mass number. And so you put that as a superscript in the top left. And then the atomic number, 26, is iron is number 26. Atomic number is 26. And so you put it as a subscript right below that. But anyway, so let's calculate the number of protons, neutrons, and electrons in this element. So anyways, the number of protons is the same as the atomic number, so that's going to be 26. This is a neutral atom, no charge. So number of electrons is the same as the number of, and the number of neutrons, you remember, is the mass number minus the atomic number. So 55 minus 26, 29, an isotope of iron, not the only one. And remember, so the mass number here is 55. So it's saying there's exactly 55 protons and neutrons. It's not a weighted average, like you find on the periodic table.