Question

In which of the following the election gain enthalpy of elements is correctly arranged?

• A. S > Se > Te > O
• B. F > Cl > Br > I
• C. Na > Li > K > Rb
• D. O > S > Se > Te

Answer 1

Answer: (A)

S > Se > Te > O

Answer 2

On moving down the group electron gain enthalpy decreases. Oxygen due to its small size causes electron-electron repulsions in relatively small $2p$ -subshell. Hence, incoming electrons cannot allow to enter easily, as in case of other elements of this group that's why oxygen has the lowest electron gain enthalpy.

Therefore, correct order of electron gain enthalpy,

$S >\, Se >\, Te >\, O$