question_answer

The d-electron configurations 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? (At. no. Cr = 24, Mn = 25, Fe = 26, Co = 27)

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 behavior.