Question

Magnetic moment 2.84B.M. is given by (Atomic number, Ni=28,Ti=22,Cr=24,Co=27)
1)Cr²+. 2)Co²+. 3)Ni²+. 4)Ti³+.

Answer 1

Formula

Magnetic moment =

$\sqrt{n(n + 2)}$

where, n = no. of unpaired electron

Trick

Given, Magnetic moment = 2.84

No. of unpaired electron = [ magnetic moment ] ( where [.] ) denotes the greatest integer function)

Hence, no. of unpaired electron = 2.

Now,electronic configuration of

• Cr²+ = 1s² 2s² 2p6 3s²3p6 3d4 (it contains four unpaired electron)

• Co²+ = 1s² 2s² 2p6 3s² 3p6 3d7 ( it contains three unpaired electron )

• Ni²+ = 1s² 2s² 2p6 3s² 3p6 3d8 (it contains two unpaired electron )

Hence, the answer is (C) Ni²+