#thelabmemories When you look at the periodic table you will see that each element has its own box and within that box, you'll find two numbers the atomic number (proton number) and the mass number. But what do these numbers mean? ✅the atomic number has a symbol Z: this number tells you how many protons are in one atom of an element ✅the mass number has a symbol A: the mass number tells you how many protons and neutrons are in one atom of an element