Doubtify – JEE Ki Taiyaari, Simple Bhasha Mein

  ❓ Question The extra stability of half-filled subshells is due to which of the following factors? Options: (A) Symmetrical distribution of electrons (B) Smaller Coulombic repulsion energy (C) Presence of electrons with same spin in non-degenerate orbitals (D) Larger exchange energy (E) Relatively smaller shielding of electrons by one another 🖼️ Question Image ✍️ Short Solution We often see exceptions in electronic configurations, like: Cr:  [ Ar ]   3 d 5   4 s 1 instead of  [ Ar ]   3 d 4   4 s 2 \text{Cr: } [\text{Ar}]\,3d^5\,4s^1 \quad \text{instead of } [\text{Ar}]\,3d^4\,4s^2 Cu:  [ Ar ]   3 d 10   4 s 1 instead of  [ Ar ]   3 d 9   4 s 2 \text{Cu: } [\text{Ar}]\,3d^{10}\,4s^1 \quad \text{instead of } [\text{Ar}]\,3d^9\,4s^2 This happens because half-filled (d⁵) and fully-filled (d¹⁰) subshells are more stable than uneven ones. Let’s understand why . 🔹 Step 1 — Symmetrical distribution of electrons In a half-filled subsh...