BCECE Medical BCECE Medical Solved Papers-2014

  • question_answer
    Peroxide ion............
    (i) has five completely filled antibonding molecular orbitals
    (ii) is diamagnetic
    (iii) has bond order one
    (iv) is isoelectronic with neon
    Which one of these is correct?

    A)  (ii) and (in)          

    B)  (i), (ii) and (iv)

    C)  (i), (ii) and (iii)       

    D)  (i) and (iv)

    Correct Answer: A

    Solution :

    Peroxide ion is \[O_{2}^{2-}\] \[O_{2}^{2-}(18)=\sigma 1{{s}^{2}},\,\,\,\,\overset{*}{\mathop{\sigma }}\,1{{s}^{2}},\,\,\,\,\sigma 2{{s}^{2}},\,\,\,\,\overset{*}{\mathop{\sigma }}\,2{{s}^{2}},\,\,\,\,\sigma 2p_{z}^{2}\], \[\pi 2p_{x}^{2}\approx 2p_{y}^{2},\,\overset{*}{\mathop{\pi }}\,2p_{x}^{2}\approx \overset{*}{\mathop{\pi }}\,2p_{y}^{2}\] Bond order \[=\frac{{{N}_{b}}-{{N}_{a}}}{2}=\frac{10-8}{2}=1\] It contains four completely filled antibonding molecular orbitals. Since, all the electrons are paired, \[O_{2}^{2-}\] is diamagnetic. Peroxide ion is isoelectronic with argon, not with neon.


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