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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+}

 
Answers (1)
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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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