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

S orbital.

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

Group 2 elements have a general configuration of . For example, Magnesium has as its outer shell configuration while Strontium has the same as .

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

answer; equivalent to a one(1) horsepower motor;