question_answer

Which one of the following complex ions has the highest magnetic moment?

A)  \[{{[Cr{{(N{{H}_{3}})}_{6}}]}^{3+}}\]

B) \[{{[Fe{{(CN)}_{6}}]}^{3-}}\]

C)  \[{{[Fe{{(CN)}_{6}}]}^{4-}}\]

D)  \[{{[Zn{{(N{{H}_{3}})}_{6}}]}^{2+}}\]

Correct Answer: A

Solution :

 Higher the number of unpaired electrons, higher is the magnetic moment. \[{{[Cr{{(N{{H}_{3}})}_{6}}]}^{3+}},Cr\]is present as \[C{{r}^{3+}}.\]Thus, In\[{{[Fe{{(CN)}_{6}}]}^{3-}},\]one unpaired electron is present and in \[{{[Fe{{(CN)}_{6}}]}^{4-}}\] and\[{{[Zn{{(N{{H}_{3}})}_{6}}]}^{2+}}\] both unpaired electrons are absent. Hence,\[{{[Cr{{(N{{H}_{3}})}_{6}}]}^{3+}}\]has the highest magnetic moment  among the given complex ions. \[[\mu =\sqrt{3(3+2)}=3.87BM].\](\[C{{N}^{-}}\] is a strong field ligand, thus causes pairing.)