Spin only magnetic moment 2 .84   BM is given by: (Atomic Number of Ni =28, Ti =22, Cr =24, Co =27 )

Step-by-step solution

μ = n ( n + 2 ) = 2.84 ⇒ n = 2 electronic configuration of Ni + 2 = 1 s 2 2 s 2 2 p 6 3 s 2 3 p 6 3 d 8 e − having two unpaired electrons electron configuration of T i 3 + = 1 s 2 2 s 2 2 p 6 3 s 2 3 p 6 3 d 1 only one unpaired electron electron configuration of C r 2 + = 1 s 2 2 s 2 2 p 6 3 s 2 3 p 6 3 d 4 having four unpaired electrons electron configuration of C o + 2 = 1 s 2 2 s 2 2 p 6 3 s 2 3 p 6 3 d 7 having three unpaired electrons.