# What is the formula for the ion formed when oxygen obtains a noble gas configuration?

An oxygen atom will gain electrons in order to achieve the electron configuration of the noble gas at the end of its period, which is neon. The electron configuration of a neutral oxygen atom is ${\text{1s"^2"2s"^2"2p}}^{4}$. The electron configuration of the noble gas neon is ${\text{1s"^2"2s"^2"2p}}^{6}$. An oxygen atom must gain two electrons in order to obtain the noble gas configuration of neon, with an octet of valence electrons. The resulting oxide ion has a charge of ${\text{2}}^{-}$, and its formula is ${\text{O}}^{2 -}$.