Spin only magnetic moment, ${\mathrm{\mu }}_{\mathrm{s}}=\sqrt{\mathrm{n}\left(\mathrm{n}+2\right)} \mathrm{B}.\mathrm{M} ; \mathrm{n}=\mathrm{number} \mathrm{of} \mathrm{unpaired} \mathrm{electrons} ;$

One B.M (Bohr Magneton) = 9.273$\times$10^-24 A.m² ;

Sc³⁺, Ti⁴⁺, Cu⁺, Zn²⁺…..n=0, ${\mathrm{\mu }}_{\mathrm{s}}=0 ;$ Diamagnetic

Ti³⁺, Cu²⁺…..n=1, ${\mathrm{\mu }}_{\mathrm{s}}=\sqrt{3}=1.732 \mathrm{B}.\mathrm{M}=1.732\times 9.273\times {10}^{-24} \mathrm{A}.{\mathrm{m}}^2 ;$

Ti²⁺, V³⁺, Ni²⁺…..n=2, ${\mathrm{\mu }}_{\mathrm{s}}=\sqrt{8}=2.82 \mathrm{B}.\mathrm{M}=2.82\times 9.273\times {10}^{-24} \mathrm{A}.{\mathrm{m}}^2 ;$

Cr³⁺, V²⁺,Co²⁺…..n=3, ${\mathrm{\mu }}_{\mathrm{s}}=\sqrt{15}=3.87 \mathrm{B}.\mathrm{M}=3.87\times 9.273\times {10}^{-24} \mathrm{A}.{\mathrm{m}}^2 ;$

Co³⁺, Fe²⁺, Mn³⁺, Cr²⁺…..n=4, ${\mathrm{\mu }}_{\mathrm{s}}=\sqrt{24}=4.9 \mathrm{B}.\mathrm{M}=4.9\times 9.273\times {10}^{-24} \mathrm{A}.{\mathrm{m}}^2 ;$

Fe³⁺, Mn²⁺…..n=5, ${\mathrm{\mu }}_{\mathrm{s}}=\sqrt{35}=5.9 \mathrm{B}.\mathrm{M}=5.9\times 9.273\times {10}^{-24} \mathrm{A}.{\mathrm{m}}^2 ;$

${\mathrm{\mu }}_{\mathrm{obs}}>{\mathrm{\mu }}_{\mathrm{cal}} ......{\mathrm{Fe}}^{2+}, {\mathrm{Co}}^{2+}, {\mathrm{Ni}}^{2+} ; \mathrm{In} \mathrm{these} \mathrm{cases} \mathrm{orbital} \mathrm{contributon} \mathrm{cannot} \mathrm{be} \mathrm{ignored}.$