# Which periodic group forms +1 ; +2 and -1 ions?

Respectively, $\text{Group 1}$, $\text{Group 2}$, and $\text{Group 17}$.
$\text{Group 1}$ metals, the alkali metals, have the 1 valence electron, and thus form ${M}^{+}$ ions when oxidized. $\text{Group 2}$ metals, the alkaline earth metals, have 2 valence electrons, and thus form ${M}^{2 +}$ ions. The halogens, $\text{Group 17}$, reach a full valence shell upon reduction, and thus form ${X}^{-}$ ions.