Question

Why is the electron gain enthalpy of $O$ or $F$ less than that of $S$ or $Cl$?

• A. O and F are more electronegative than S and Cl.
• B. When an electron is added to O or F, it goes to a smaller $(n = 2)$ level and suffers more repulsion than the electron in S or Cl in larger level $(n = 3)$.
• C. Adding an electron to 3p-orbital leads to more repulsion than 2p-orbital.
• D. Electron gain enthalpy depends upon the electron affinity of the atom.

Answer 1

Answer: (B)

When an electron is added to O or F, it goes to a smaller $(n = 2)$ level and suffers more repulsion than the electron in S or Cl in larger level $(n = 3)$.

Answer 2

There is more repulsion for the incoming electron when the size of atom is smaller.