JEE Main & Advanced Chemistry Chemical Bonding and Molecular Structure / रासायनिक आबंधन एवं आणविक संरचना Sample Paper Topic Test - Chemical Bonding

  • question_answer
    Which of the following is correct regarding ionization potential?

    A) \[O_{2}^{2+}>NO\]

    B) \[O_{2}^{2+}<NO\]

    C) \[O_{2}^{{}}<NO\]

    D) \[O_{2}^{2+}=NO\]

    Correct Answer: A

    Solution :

    [a] Idea
    This problem includes conceptual mixing of ionisation potential and Molecular Orbital Electronic Configuration (MOEC) of molecule.
    In order to solve this problem students are advised to write MOEC of molecules/ions. If molecular orbital contain unpaired electron in vacant MO, then it will be loosed easily hence have low value of ionisation energy.
    MOEC of \[O_{2}^{--}=\sigma _{1s}^{2}\sigma _{1s}^{*\,2}\sigma _{2s}^{2}\sigma _{2s}^{*\,2}\sigma _{2{{p}_{z}}}^{2}\]
    \[(\pi _{1\pi x}^{2}\equiv \pi _{2{{p}_{y}}}^{\,2})({{\pi }^{*}}_{2{{p}_{x}}}^{2}\equiv {{\pi }^{*}}_{2{{p}_{y}}}^{\,2})\]
    All electrons are paired hence it is diamagnetic and will not electron easily MOEC of \[{{O}_{2}}={{\sigma }^{*}}_{1s}^{2}{{\sigma }^{*}}_{2s}^{2}\sigma _{2{{p}_{z}}}^{2}\]
    \[(\pi _{2{{p}_{x}}}^{2}\equiv \pi _{2{{p}_{y}}}^{\,2})\,\,\,\,(\pi _{2{{p}_{x}}}^{1}\equiv \pi _{2{{p}_{y}}}^{\,1})n=2\]
    Hence it can loose electron more easily due to presence of two electron having identical energy Ionization potential Molecule having available unpaired valence electron in molecular orbital looses electron easily electron show less value of ionization potential
    MOEC of \[O_{2}^{2+}=\sigma _{1s}^{2}{{\sigma }^{*}}_{1s}^{2}\sigma _{2s}^{2}{{\sigma }^{*}}_{2s}^{2}\sigma _{2{{p}_{z}}}^{2}\pi _{2{{p}_{x}}}^{2}\equiv \pi _{2py}^{2}\]
    All electrons are paired in molecular orbitals hence is diamagnetic
    MOEC of \[NO=\sigma _{1s}^{2}\sigma _{1s}^{*2}\sigma _{2s}^{*2}\sigma _{2{{p}_{z}}}^{2}\pi _{2{{p}_{x}}}^{2}\equiv \pi _{2{{s}_{y}}}^{2}\]\[\pi _{2{{p}_{x}}}^{*1}=\pi _{2{{p}_{y}}}^{*}\]
    Since, NO has unpaired electron present in antibonding molecular orbital \[\pi _{2{{p}_{x}}}^{*},\] hence it will loose the electron easily.
    TEST Edge In JEE Main, similar question having conceptual mixing of MOEC and colour of molecules ion are asked, so students are advised to understand the colour as well as stability of molecules/ions using MOEC in a clear way.


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