question_answer

The    d-electron    configuration    of\[C{{r}^{2+}},M{{n}^{2+}},F{{e}^{2+}}\] and\[C{{o}^{2+}}\] are \[{{d}^{4}},{{d}^{5}},{{d}^{6}}\]and\[{{d}^{7}}\] respectively. Which one of the following will exhibit minimum paramagnetic behaviour? \[\left[ At.no.Cr=24,Mn=25,Fe=26,Co=27 \right]\]

A) \[{{[Fe{{({{H}_{2}}O)}_{6}}]}^{2+}}\]      

B) \[{{[Co{{({{H}_{2}}O)}_{6}}]}^{2+}}\]

C) \[{{[Cr{{({{H}_{2}}O)}_{6}}]}^{2+}}\]       

D) \[{{[Mn{{({{H}_{2}}O)}_{6}}]}^{2+}}\]

Correct Answer: B

Solution :

\[\therefore \]\[{{[Co{{({{H}_{2}}O)}_{6}}]}^{2+}}\]has minimum number of unpaired electrons and thus minimum paramagnetic behaviour.