KVPY Sample Paper KVPY Stream-SX Model Paper-15

  • question_answer
    Which of the following species is not paramagnetic'

    A) \[NO\]

    B) \[CO\]

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

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

    Correct Answer: B

    Solution :

    Those species, which have one or more than one unpaired electron, are paramagnetic in nature. The electronic configuration of given species are as follows:
    [a] \[NO=15\]
    \[=\sigma 1s_{,}^{2}{{\sigma }^{*}}1s_{,}^{2}\sigma 2s_{,}^{2}{{\sigma }^{*}}2{{s}^{2}}\sigma 2p_{z}^{2}\pi 2p_{x}^{2}=\pi 2p_{y}^{2}{{\pi }^{*}}2p_{x}^{1}\]
    [b] \[CO=14\]
    \[1{{s}^{2}}{{\sigma }^{*}}1{{s}^{2}}\sigma 2{{s}^{2}}{{\sigma }^{*}}2{{s}^{2}}\sigma 2p_{z}^{2}\pi 2p_{x}^{2}=\pi 2p_{y}^{2}\]
    [c] \[{{O}_{2}}=16=\sigma 1{{s}^{2}}\sigma *1{{s}^{2}}\sigma 2{{s}^{2}}\sigma *2{{s}^{2}}\sigma 2p_{z}^{2}\]
    \[\pi 2p_{x}^{2}=\pi 2p_{y}^{2}\pi *2p_{x}^{1}=\pi *2p_{y}^{1}\]
    [d]\[{{B}_{2}}=10=\sigma 1{{s}^{2}}\sigma *1{{s}^{2}}\sigma 2{{s}^{2}}\sigma *2{{s}^{2}}\pi 2p_{x}^{1}=\pi 2p_{y}^{1}\]
    As all the electrons in \[CO\]are paired, so it is not a paramagnetic species.


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