Question

Arrange $\mathrm{S},\mathrm{O}$ and $\mathrm{Se}$ in ascending order of electron affinity.

• A. $Se<S<O$
• B. $Se<O<S$
• C. $S<O<Se$
• D. $S<Se<O$

Answer 1

The correct option is A

$\mathrm{Se}<\mathrm{S}<\mathrm{O}$

Explanation for correct option:

(A) $\mathbf{Se}\mathbf{<}\mathbf{S}\mathbf{<}\mathbf{O}$:

Electron affinity:

• When an electron is added to a neutral atom to produce a negatively charged ion, the amount of energy released is called electron affinity.
• The electron affinity typically decreases down a group.

The ascending order of electron affinity of $\mathbf{S}\mathbf{,}\mathbf{}\mathbf{O}$ and $\mathbf{Se}$:

• $\mathrm{S},\mathrm{O}$ and $\mathrm{Se}$ are all elements of the ${16}^{\mathrm{th}}$ group.
• The electron affinity of a group decreases as the atomic number increases.
• The correct order of electron affinity is $\mathrm{Se}<\mathrm{S}<\mathrm{O}$.

Hence, (A) is the correct option.

Explanation for incorrect options:

Since, the correct ascending order of electron affinity is $\mathrm{Se}<\mathrm{S}<\mathrm{O}$. Therefore, all the other options (B), (C) and (D) are incorrect.

Therefore, the correct option is (A) $\mathbf{Se}\mathbf{<}\mathbf{S}\mathbf{<}\mathbf{O}$.