![[FeCl4]2− (I), [CoCl4]2− (II) and [NiCl4]2− (III) are paramagnetic tetrahedral complexes. Q.22 The order of values of crystal field stabilization energy is (A) I > III > II (B) III > I > II (C) I > II > III (D) II > III > I](https://www.letstalkacademy.com/wp-content/uploads/2026/01/slide_22-8.jpg)
[FeCl4]2− (I), [CoCl4]2− (II) and [NiCl4]2− (III) are paramagnetic tetrahedral complexes.
Q.22 The order of values of crystal field stabilization energy is
Key Concept: CFSE in Tetrahedral Complexes
- Tetrahedral complexes have smaller crystal field splitting.
- All tetrahedral complexes are high spin.
- Orbital splitting pattern:
- e (lower energy) = −0.6Δt
- t2 (higher energy) = +0.4Δt
- CFSE depends on d-electron configuration.
Oxidation State and d-Electron Count
(I) [FeCl4]2−
Oxidation state of Fe = +2 → d6
(II) [CoCl4]2−
Oxidation state of Co = +2 → d7
(III) [NiCl4]2−
Oxidation state of Ni = +2 → d8
CFSE Calculations
CFSE Formula:
CFSE = (electrons in e × −0.6Δt) + (electrons in t2 × +0.4Δt)
(I) Fe2+ (d6)
Electron configuration: e4 t22
CFSE = −1.6Δt
(II) Co2+ (d7)
Electron configuration: e4 t23
CFSE = −1.2Δt
(III) Ni2+ (d8)
Electron configuration: e4 t24
CFSE = −0.8Δt
Order of CFSE
Greater negative CFSE value means greater stabilization.
I > II > III
Correct Answer
✅ Option (C): I > II > III
Explanation of All Options
Option (A): I > III > II
❌ Incorrect. d8 has less CFSE than d7.
Option (B): III > I > II
❌ Incorrect. d8 tetrahedral complexes have the least CFSE.
Option (C): I > II > III
✔ Correct. CFSE decreases as d-electrons increase from d6 to d8.
Option (D): II > III > I
❌ Incorrect. Fe2+ (d6) has maximum CFSE.
