JEE Main & Advanced Sample Paper JEE Main - Mock Test - 15

  • question_answer
    According to MO theory which of the following lists ranks the nitrogen species in terms of increasing bond order?

    A) \[N_{2}^{2-}<N_{2}^{-}<{{N}_{2}}\]

    B) \[{{N}_{2}}<N_{2}^{2-}<N_{2}^{-}\]

    C) \[N_{2}^{-}<N_{2}^{2-}<{{N}_{2}}\]  

    D) \[N_{2}^{-}<{{N}_{2}}<N_{2}^{2-}\]

    Correct Answer: A

    Solution :

    Molecular orbital configuration of
    \[N_{2}^{2-}=\sigma 1{{s}^{2}}\sigma *1{{s}^{2}}\sigma 2{{s}^{2}}\sigma *2{{s}^{2}}\,\,\,\,\sigma 2p_{z}^{2}\]
    \[\pi 2p_{x}^{2}=\pi 2p_{y}^{2}\,\pi *2p_{x}^{1}=\pi *2p_{y}^{1}\]
    Bond order \[=\frac{10-6}{2}=2\]
    \[N_{2}^{-}=\sigma 1{{s}^{2}}\sigma *1{{s}^{2}}\sigma 2{{s}^{2}}\sigma *2{{s}^{2}}\,\,\,\sigma 2p_{z}^{2}\]
    \[\pi 2p_{x}^{2}=\pi 2p_{y}^{2}\pi *2p_{x}^{1}=\pi *2p_{y}^{0}\]
    Bond order \[=\frac{10-5}{2}=2.5\]
    \[{{N}_{2}}=\sigma 1{{s}^{2}}\sigma *1{{s}^{2}}\sigma 2{{s}^{2}}\sigma *2{{s}^{2}}\pi 2p_{x}^{2}=\pi 2p_{y}^{2}\,\sigma 2p_{z}^{2}\]
    Bond order \[=\frac{10-4}{2}=3\]
    \[\therefore \]  The correct order is \[N_{2}^{2-}<N_{2}^{-}<{{N}_{2}}\]


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