Question

Electrons are added into the outermost what in groups 1 & 2

Answer 1

S orbital.

Group 1 elements have a general configuration $ns^{1}$, where n represents the highest occupied Principal Energy Level. For example, Lithium has the valence configuration $2s^{1}$ whereas Cesium has $6s^{1}$. Both of them belong to Group 1 of Periodic Table.

Group 2 elements have a general configuration of $ns^{2}$. For example, Magnesium has $3s^{2}$ as its outer shell configuration while Strontium has the same as $5s^{2}$.

We see that in both the cases, the outermost S orbital is being filled.