Question

Which of the following relation is true for high negative value of electron gain enthalpy?

• A. F < Cl
• B. B < Be
• C. C < N
• D. C < B

Answer 1

The correct option is A F < Cl

As we move from left to right in a period, electron gain enthalpy increases and as we move from top to bottom in a group, electron gain enthalpy decreases. But, C and N are exceptions (along the period) due to stable half - filled elecronic configuration of N. It's tough to accept an electron. Hence electron gain enthalpy of N < C. As per general trend, Be < B and B < C. Down the group, electron gain enthalpy decreases but F < Cl due to small size of fluorine atom, there are strong interelectronic repulsions in the relatively small 2p orbitals of fluorine and thus, the incoming electron does not experience much attraction.