# Why do the members of Group 1 react by losing an electron, but the members of Group 17 react by gaining an electron?

Jun 23, 2018

Because metals are reducing....

#### Explanation:

And non-metals are oxidizing...

Consider the electronic structure of the alkali metals. These have a SINGLE valence electron...and are readily oxidized..

$N a \left(s\right) \rightarrow N {a}^{+} + {e}^{-}$

On the other hand, non metals, i.e. dioxygen, difluorine, and dichlorine, have high unshielded nuclear charge, and certainly this is reflected by the atomic radii...WHICH DECREASE ACROSS a Period, from left to right as we face the Table.....

And thus the halogens have high UNSHIELDED nuclear charge, and are very readily reduced .... to give FORMALLY LARGER ANIONS, i.e. ${O}^{2 -}$, ${S}^{2 -}$, and ${X}^{-}$...

$\frac{1}{2} {X}_{2} + {e}^{-} \rightarrow {X}^{-}$

And so the relative reactivities owe to atomic structure, which is certainly reflected by the Periodic Table....