CBSE Class 12 · 2003 · Delhi · Coordination CompoundsShort Answer

Using the valence bond approach, predict the shape and magnetic character of the [Fe(CN)

_{6}

]

^{3 -}

ion. (Atomic number of Fe = 26)

Answer: Octahedral, d²sp³ (inner orbital); paramagnetic with 1 unpaired electron (low spin).

Solution

Fe oxidation state: x + 6(−1) = −3 ⇒ Fe

^{3 +}

= 3d

^{5}

.
CN

^{-}

(strong field) pairs the electrons: t

_{2 g}^{5}

— one unpaired electron; two 3d orbitals vacate for d

^{2}

^{3}

.
Shape: octahedral (inner-orbital, low-spin).
Magnetism: 1 unpaired electron → weakly paramagnetic, μ = √3 ≈ 1.73 BM.

CBSE Class 12 Board · 2003 · Delhi · Subjective