Question

Which among the following pairs of elements in their respective oxidation states will have same value of effective magnetic moment?
(Atomic number: Sc = 21, Ti = 22, Cr = 24, Co = 27, Ni = 28, Zn = 30)

Options

• Zn²⁺ and Cr³⁺

• Ni²⁺ and Ti³⁺

• Sc³⁺ and Ti³⁺

• Cr³⁺ and CO²⁺

Answer 1

Cr³⁺ and CO²⁺ 

Explanation:

Configuration		No. of unpaired electrons
Sc3+ = 4s0 3d0		0
Cr3+ = 4s0 3d3		3
Ti3+ = 4s0 3d1		1
Ni2+ = 4s0 3d8		2
Co2+ = 4s0 3d7		3

Species having same number of unpaired electrons have same dipole moment:

Cr³⁺ & CO²⁺ have 3 unpaired electrons.

`mu = sqrt("n"("n + 2")) = sqrt15` = 3.9