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.