The extra stability of half-filled subshell is due to : Identify the correct statements :
- B, D and E only
- A, B, D and E only
- B, C and D only
- A, B and D only
Answer
(2) A, B, D and E only
Solution
As per NCERT, half-filled and completely filled subshells are extra stable because of:
(A) Symmetrical distribution of electrons — symmetry leads to stability. Correct.
(D) Larger exchange energy — electrons with parallel spins in degenerate orbitals can exchange positions; the number of exchanges is maximum in half-filled subshells. Correct.
(E) Electrons in the same subshell have equal energy but different spatial distribution, so their shielding of one another is relatively small and they are more strongly attracted by the nucleus. Correct.
(B) Parallel-spin electrons tend to stay apart, so the coulombic repulsion energy is smaller. Correct.
(C) The electrons with the same spin are in degenerate (not non-degenerate) orbitals. Incorrect.
A, B, D and E are correct.
Answer: (2)