# If an atom has a charge of -2 and an atomic number of 7, how many electrons does it have?

The atomic number for an element is the number of protons in the nuclei of their atoms. In a neutral atom, there are equal numbers of protons and electrons. Since the atom has gained a charge of $\text{2-}$, it now has two more electrons than protons. So the number of electrons is now $9$.
$\text{9e"^(-) + 7p^(+) = 2e^-}$