CBSE Class 12 · 2000 · Delhi · Coordination CompoundsShort Answer

Using the valence bond theory, predict the shape and magnetic behaviour of the [Cr(NH

_{3}

)

_{5}

Cl]

^{2 +}

ion. [Atomic number of Cr = 24]

Answer: Octahedral (d²sp³); paramagnetic with 3 unpaired electrons (μ ≈ 3.87 BM).

Solution

Cr oxidation state: x + 0 + (−1) = +2 ⇒ Cr

^{3 +}

= [Ar]3d

^{3}

.
The three d electrons occupy three 3d orbitals singly; two empty 3d + one 4s + three 4p give d

^{2}

^{3}

hybridisation.
Shape: octahedral.
Magnetic behaviour: 3 unpaired electrons → paramagnetic,

μ = 3 \times 5 = 15 \approx 3.87 BM

CBSE Class 12 Board · 2000 · Delhi · Subjective