Question

Which has maximum paramagnetic nature?

• A. $ [Fe(CN)_{6}]^{4-} $
• B. $[Cu(H_{2}O)_{4}]^{2+}$
• C. $[Zn(NH_{3})_{4}]^{2+}$
• D. $[Mn(H_{2}O)_{6}]^{2+}$

Answer 1

Answer: (D)

Paramagnetic character $\propto$ number of unpaired electrons
(a) $\left[ Fe ( CN )_{6}\right]^{4-}$ Iron is in $+2$ oxidation state.

There is no unpaired electron in $\left[ Fe ( CN )_{6}\right]^{4-}$. So, it is diamagnetic.
(b) $\left[ Cu \left( H _{2} O \right)_{4}\right]^{2+}$ Copper is in $+2$ oxidation state.

There is one unpaired electron. So, it is paramagnetic.
(c) $\left[ Zn \left( NH _{3}\right)_{4}\right]^{2+}$ zinc is in $+2$ oxidation state.

There is no unpaired electron. So, it is diamagnetic.
(d) $\left[ Mn \left( H _{2} O \right)_{6}\right]^{2+} Mn$ is in $+2$ oxidation state.

In $\left[ Mn \left( H _{2} O \right)_{6}\right]^{2+}$ there are five unpaired electrons. So, it has maximum paramagnetic character.