# What stable ion sulfur should form based on its electron configuration?

The stable ion the sulfur would form is the sulfide ion, ${\text{S}}^{2 -}$.
A neutral sulfur atom contains 16 electrons. We can know this because its atomic number is 16, which means there are 16 protons in the nucleus. Since the negative charge of the electrons cancels the charge of the protons, the sulfur atom is neutral. The electron configuration of sulfur is $\text{1s"^2"2s"^2"2p"^6"3s"^2"3p"^4}$. The valence shell (the 3s and 3p sublevels) contains six electrons, but it needs eight to become stable. Think of the octet rule. Therefore a sulfur atom will gain two electrons to form the sulfide anion with a charge of ${2}^{-}$, with the symbol ${\text{S}}^{2 -}$.