# When a nonmetal atom gains (an) electron(s), what does it become?

For example, Chlorine $\left(C l\right)$ gains an electron to become $C {l}^{-}$ as it has gone from having 17 electrons as chlorine, 7 of which are valence electrons, and 17 protons - equal numbers so overall charge is zero - to having 18 electrons as the chloride ion - 8 valence electrons. 18 negative electrons compared with 17 positive protons means the ion is negatively charged.