Q. Which one of the following cyano complexes would exhibit the lowest value of paramagnetic behaviour? (Atomic no. Cr=24, Mn=25, Fe=26, Co=27)
A) $\left\lbrack Co(CN)_{6} \right\rbrack^{3 -}$
B) $\left\lbrack Fe(CN)_{6} \right\rbrack^{3 -}$
C) $\left\lbrack Mn(CN)_{6} \right\rbrack^{3 -}$
D) $\left\lbrack Cr(CN)_{6} \right\rbrack^{3 -}$
Explanation
(a)
[table] | Hybridization | Unpaired
electrons | Magnetic
moment ; 1.$\left\lbrack Co(CN)_{6} \right\rbrack^{3 -}$ | $d^{2}sp^{3}$ | 0 | 0 ; 2.$\left\lbrack Fe(CN)_{6} \right\rbrack^{3 -}$ | $d^{2}sp^{3}$ | 1 | $\sqrt{3}$ BM ; 3. $\left\lbrack Mn(CN)_{6} \right\rbrack^{3 -}$ | $d^{2}sp^{3}$ | 2 | $\sqrt{8}$ BM ; 4.$\left\lbrack Cr(CN)_{6} \right\rbrack^{3 -}$ | $d^{2}sp^{3}$ | 3 | $\sqrt{15}$ BM [/table]
Thus, least paramagnetism is in (a).
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.