# What is the mass in grams of one mole of the element containing 12 protons?

Well, if it has got 12 protons, then $Z = 12$.........
And if $Z = 12$, then we gots the element magnesium. Now of course a magnesium atom contains not only the 12 protons; it also contains 12-13 neutrons, massive, UNCHARGED, nuclear particles.
And so we have a mass of $24.3 \cdot g$. How did I know this mass? Well, I have access to a Periodic Table. Is there one by your side?