Question

Two non-metallic elements X and Y have L and M shells as valence shells respectively with same no. of electrons. Compare the electron affinity values of X and Y.

Answer 1

Two non- metallic elements X and Y have L and M shells as valence shells respectively with same number of electrons. X and Y belong to the group 13 and 17 and period 2 and 3 respectively

As we descend the group, ( from X to Y) , electron affinity generally decreases.

Reason:

Each atom​ ​is larger than the atom above it (this is the atomic radius trend). This means that an added electron is further away from the atom’s nucleus compared with its position in smaller atom. With a larger distance between the negatively charged electron and the positively charged nucleus, the force of attraction is relatively weaker. Therefore electron affinity decreases.