TS EAMCET 19-July-2022 Shift 1 Solved Paper

On moving down the group, from S to Se electron gain enthalpy decreases. Oxygen has an unexpectedly low value of electron gain enthalpy. This is because of smaller size of oxygen atom due to which incoming electron faces more electronic repulsions which decreases its electron affinity. So, the correct order is O>Se>S.

Se→−195.5‌kJ‌mol−1

S→−208.8‌kJ‌mol−1

O→−141.4‌kJ‌mol−1

}‌electron gain enthalpy