NEET Sample Paper NEET Sample Test Paper-25

  • question_answer
    Atomic numbers of Cr and Fe are respectively 24 and 26. Which of the following is paramagnetic with the spin of the electron?

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

    B) \[[Fe{{(CO)}_{5}}]\]

    C) \[{{[Fe{{(CN)}_{6}}]}^{4-}}\]             

    D) \[[Cr{{(CO)}_{6}}]\]    

    Correct Answer: A

    Solution :

    \[{{[Fe{{(CN)}_{6}}]}^{4}}^{-}\] is diametric  (\[F{{e}^{2+}}\]has\[3{{d}^{6}}\]configuration and the 6 electro airs up in three d-orbitals followed by (\[{{d}^{2}}s{{p}^{3-}}\]hybridization). \[{{[Cr{{(N{{H}_{3}})}_{6}}]}^{3+}}\]is paramagnetic (\[C{{r}^{3+}}\]has \[3{{d}^{3}}\] con-figuration. Hybridization is \[{{d}^{2}}s{{p}^{3}}.\]Due to 3 unpaired electrons it is paramagnetic) \[[Cr{{(CO)}_{6}}:Cr(Z=25):{{[Ar]}^{18}}4{{s}^{1}},3{{d}^{5}}.\] The one 4s-electron pairs up with five 3d-electrons in three (d-orbitals. This is followed by \[{{d}^{2}}s{{p}^{3}}-\]hybridization to give octahedral complex. No unpaired electron and hence complex is diamagnetic. \[Fe{{(CO)}_{5}}:Fe(Z=26):{{[Ar]}^{18}}4{{s}^{2}},3{{d}^{6}}.\] The six electrons in o'-subshell pairs up in three d-orbitals. This is followed by \[{{d}^{2}}s{{p}^{3}}-\]hybridization to give octahedral geometry with one vacant hybridized orbital. The resulting shape of the complex is square-based pyramid. As there is no unpaired. electron, the complex is diamagnetic.


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