Spin only mangnetic moment is given as μS=√n(n+2)BM where, n = number of unpaired electrons Electronic configuration of mathrmB2+is as follows B2+=σ1s2,σ*1s2,σ2s2,σ*2s2,π2py1=π2pz0 ∴ B2+ has one unpaired electron, μ=√1(1+2)=√3=1.73BM =173×10−2BM ∴x×10−2=173×10−2 ∴ x = 173 Hence, answer is 173.