An element X has two isotopes, which may be represented as ${}^{238}\mathrm{X}$  and ${}^{235}\mathrm{X}$. How does ${}^{238}\mathrm{X}$ differ from ${}^{235}\mathrm{X}$?

It has 3 more neutrons and 3 more electrons

It has 3 more protons but no more electrons

It has 3 more neutrons but no more electrons

It has 3 more protons and 3 more electron