JEE Chemistry 2025 Question with Solution

Given: The question asks which statements explain the extra stability of a half-filled subshell.

Find: Identify the correct set of statements.

From the solution text:

1. Symmetrical distribution of electrons contributes to stability because the electron distribution is more balanced.
2. Smaller coulombic repulsion energy is valid because electrons are distributed as evenly as possible, reducing repulsion.
3. Statement (C) is not taken as the primary reason for extra stability. It describes Hund's rule, but that alone is not the special stabilizing factor being asked here.
4. Larger exchange energy is a major reason for extra stability.
5. Relatively smaller shielding of electrons by one another also contributes to stability according to the provided solution.

Therefore, the correct statements are (A), (B), (D) and (E) only.

So, the correct option is B.

The solution explicitly states that half-filled subshells are stabilized by symmetrical distribution, reduced coulombic repulsion, larger exchange energy, and relatively smaller shielding, while statement (C) is excluded.

Given: A half-filled subshell shows extra stability.

Find: Which among statements (A) to (E) are responsible.

Evaluate each statement:

• (A) Symmetrical distribution of electrons: A half-filled subshell has a balanced arrangement of electrons. This symmetry is associated with greater stability.
• (B) Smaller coulombic repulsion energy: When electrons occupy different orbitals singly, electron-electron repulsion is minimized compared to less symmetric arrangements.
• (C) The presence of electrons with the same spin in non-degenerate orbitals: This reflects the filling pattern, but the provided solution does not treat it as the direct reason for the extra stability being asked.
• (D) Larger exchange energy: A half-filled subshell has maximum possible exchange energy, which lowers the energy and increases stability.
• (E) Relatively smaller shielding of electrons by one another: The provided solution includes this as a contributing factor.

Hence the correct combination is (A), (B), (D) and (E) only, which corresponds to option B.

Therefore, the correct option is B.