Consider the following complexes:

Question

[Fe(H₂O)₆]²⁺
[Fe(CN)₆]³⁻
[Fe(CN)₆]⁴⁻
[Fe(H₂O)₆]³⁺

Which one of the following is the correct order of number of unpaired electrons in the above complexes?

(a) 4 > 1 > 2 > 3
(b) 1 > 2 > 3 > 4
(c) 3 > 2 > 1 > 4
(d) 4 > 2 > 1 > 3

Vimal Swarnkar · Accepted Answer

(a) 4 > 1 > 2 > 3. 4. [Fe(H₂O)₆]³⁺ d⁵ high spin → 5. 1. [Fe(H₂O)₆]²⁺ d⁶ high spin → 4. 2. [Fe(CN)₆]³⁻ d⁵ low spin → 1. 3. [Fe(CN)₆]⁴⁻ d⁶ low spin → 0. Order 4 > 1 > 2 > 3 → (a).

Answer

(b) 1 > 2 > 3 > 4

Answer

(c) 3 > 2 > 1 > 4

Answer

(d) 4 > 2 > 1 > 3

Geo-Scientist Prelims 2020 Chemistry Q22: Consider the following complexes:

QuestionCoordination / unpaired electrons