JEE Main & Advanced Chemistry Chemical Bonding and Molecular Structure / रासायनिक आबंधन एवं आणविक संरचना Question Bank Molecular orbital theory

  • question_answer
    Which of the following is paramagnetic  [UPSEAT 2004]

    A)                 \[{{B}_{2}}\]      

    B)                 \[{{C}_{2}}\]

    C)                 \[{{N}_{2}}\]     

    D)                 \[{{F}_{2}}\]

    Correct Answer: A

    Solution :

               Paramagnetic property arise through unpaired electron. \[{{B}_{2}}\] molecule have the unpaired electron so it show paramagnetism.                    \[{{B}_{2}}\to \]\[\underset{\text{(2 unpaired electron)}}{\mathop{\sigma 1{{s}^{2}}{{\sigma }^{*}}1{{s}^{2}},\sigma 2{{s}^{2}}{{\sigma }^{*}}2{{s}^{2}},\pi 2{{p}_{x}}^{1}=\pi 2{{p}_{y}}^{1}}}\,\]                    \[{{C}_{2}}\to \] \[\underset{\text{(No unpaired electron)}}{\mathop{\sigma 1{{s}^{2}}{{\sigma }^{*}}1{{s}^{2}},\sigma 2{{s}^{2}}{{\sigma }^{*}}2{{s}^{2}},\pi 2{{p}_{x}}^{2}.\pi 2{{p}_{y}}^{2}}}\,\]                    \[{{N}_{2}}\to \] \[\underset{\text{(No unpaired electron)}}{\mathop{\sigma 1{{s}^{2}}{{\sigma }^{*}}1{{s}^{2}},\sigma 2{{s}^{2}}{{\sigma }^{*}}2{{s}^{2}},\sigma 2{{p}_{x}}^{2},\pi 2{{p}_{y}}^{2}\pi 2{{p}_{z}}^{2}}}\,\]                    \[{{F}_{2}}\to \]\[\underset{\text{(No unpaired electron)}}{\mathop{\sigma {{s}^{2}},{{\sigma }^{*}}1{{s}^{2}},\sigma 2{{s}^{2}},{{\sigma }^{*}}2{{s}^{2}},\sigma 2{{p}_{x}}^{2},\pi 2{{p}_{y}}^{2},\pi 2{{p}_{z}}^{2},}}\,\]                                                                       \[{{\pi }^{*}}2{{p}_{y}}^{2},{{\pi }^{*}}2{{p}_{z}}^{2}\]                                 So only \[{{B}_{2}}\] exist unpaired electron and show the paramagnetism.


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