The elements of which group in the periodic table release the most energy by gaining an electron? The elements of which group in the periodic table absorb the most energy when gaining an electron?

Valence shell electronic configuration for all given groups is,

1A: ns¹np⁰

2A: ns²np⁰

3A: ns²np¹

4A: ns²np²

5A: ns¹np³

6A: ns²np⁴

7A: ns²np⁵

8A: ns²np⁶

1)For 7A i.e. (Halogen family) group gain of 1 electron will make octet state complete and a stable electronic system results and hence large amount of energy will be released. Hence large amount of energy will be released 7A group elements i.e. Halogens (F, Cl, Br, I, At*) gains an electron and a very stable anion generates.

2)8A i.e. Noble gases has complete octet stable and already had very much stable arrangement. Addition of electron to this stable system will destabilize the system and to force the inert gases to accept electron will require large energy input. Hence elements of 8A group i.e. noble gases will absorb most energy when accept an electron.