# FAQ overflow

#### QUESTION

I used to be under the (wrong) assumption that the density of an element correlates with it's atomic number $\mathrm{Z}$, I thought that since having more protons meant the atom weighed more; but of course that's wrong.

So why does make osmium $\mathrm{Os}$, with an atomic number of $\mathrm{Z}_{\mathrm{Os}}=76$ more dense than say uranium $\mathrm{U}$, with an atomic number of $\mathrm{Z}_{\mathrm{U}}=92$?