Q40 of 70 Page 111

Although Cr3+ and Co2+ ions have same number of unpaired electrons but the magnetic moment of Cr3+ is 3.87 B.M. and that of Co2+ is 4.87 B.M. Why?

The electronic configuration of

Cr3+ - [Ar] 3d3


Co2+- [Ar] 3d7


Cr3+ has a symmetrical electron distribution and will only have spin magnetic moment contribution whereas Co2+ has no symmetrical distribution of electrons so it will have orbital magnetic moment and spin magnetic moment contribution. Therefore, the total magnetic moment for Co2+ will be higher than Cr3+.


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