Question 1

What is the difference between d2sp3 and sp3d2 hybridisation?

Accepted Answer

In d2sp3, two inner 3d orbitals, one 4s orbital and three 4p orbitals participate to form six hybrid orbitals. In sp3d2, one 4s orbital, three 4p orbitals and two outer 4d orbitals participate. Both give six octahedral directions and coordination number 6.

Question 2

Why does Co3+ have a d6 configuration?

Accepted Answer

Neutral cobalt has the ground-state configuration [Ar] 3d7 4s2. Removing three electrons for Co3+ removes the two 4s electrons first and then one 3d electron, leaving [Ar] 3d6.

Question 3

How do unpaired electrons affect magnetic behaviour?

Accepted Answer

Unpaired electrons produce paramagnetism because their spins create a net magnetic moment. A complex with all electrons paired is diamagnetic and is repelled by a magnetic field. The spin-only relation is μ = sqrt(n(n+2)) BM, where n is the number of unpaired electrons.

Question 4

What does dz2 look like in a three-dimensional orbital diagram?

Accepted Answer

The dz2 orbital has two lobes along the z-axis and a torus in the xy plane. The dx2-y2 orbital instead has lobes along the x and y axes, while dxy, dxz and dyz have lobes between their named axes.

Question 5

Why do d2sp3 and sp3d2 both give coordination number 6?

Accepted Answer

Each hybridisation combines six atomic orbitals to produce six directional hybrid orbitals. These point along +x, −x, +y, −y, +z and −z, so one ligand can occupy each direction and the resulting octahedral complex has coordination number 6.

Inner vs Outer Orbital: Why Some Complexes Grab a Magnet

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