Q

# Solve this problem - Coordination compounds: - NEET

The d-electron configurations of $Cr^{2+}, Mn^{2+}, Fe^{2+}$ and $Co^{2+}$ are $d^{4}, d^{5}, d^{6}$ and $d^{7}$, respectively. Which one of the following will exhibit minimum paramagnetic behaviour?
At, nos. Cr=24, Mn=25, Fe=26, Co=27)

• Option 1)

$\left [ Mn(H_{2}O)_{6} \right ]^{2+}$

• Option 2)

$\left [ Fe(H_{2}O)_{6} \right ]^{2+}$

• Option 3)

$\left [ Co(H_{2}O)_{6} \right ]^{2+}$

• Option 4)

$\left [ Cr(H_{2}O)_{6} \right ]^{2+}$

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As we learnt in

Magnetic Moments (spin only) -

$\sqrt{n\left ( n+2 \right )}$ where n= number of unpaired electron.

- wherein

Number of unpaired $e^{-} s$ and corresponding magnetic moments

$\\1\rightarrow 1.7\\2\rightarrow 2.8\\3\rightarrow 3.9\\4\rightarrow 4.9\\5\rightarrow 5.9$

$H_{2}O$  is awork field ligand.

The $e^{-}$ config of $CO^{2+}$ in the complex $\left [ C_{o}\left ( H_{2}O \right )_{6} \right ]^{2+}$  is

Similarly, for Cr2+

For Mn2+

For Fe2+

$\therefore C{O}^{2+}$  has min. no. of impaired s & a it will exchibit minimum paramagnetic behaviour.

Option 1)

$\left [ Mn(H_{2}O)_{6} \right ]^{2+}$

Incorrect Option

Option 2)

$\left [ Fe(H_{2}O)_{6} \right ]^{2+}$

Incorrect Option

Option 3)

$\left [ Co(H_{2}O)_{6} \right ]^{2+}$

Correct Option

Option 4)

$\left [ Cr(H_{2}O)_{6} \right ]^{2+}$

Incorrect Option

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