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NEET Sample Paper NEET Sample Test Paper-89

  • question_answer
    Identify the correct order of electron affinity for \[{{O}^{-}},\]\[O,\]\[{{F}^{-}}\]and \[N{{a}^{+}}.\]

    A) \[N{{a}^{+}}<{{F}^{-}}<{{O}^{-}}<O\]

    B) \[O<{{O}^{-}}<{{F}^{-}}<N{{a}^{+}}\]

    C) \[{{O}^{-}}<O<<{{F}^{-}}<N{{a}^{+}}\]

    D) \[{{F}^{-}}<N{{a}^{+}}<{{O}^{-}}<O\]

    Correct Answer: C

    Solution :

    [c]
    \[{{O}^{-}}\] \[O\] \[{{F}^{-}}\] \[N{{a}^{+}}\]
    Electrons 9 8 10 10
    Nuclear charge 8 8 9 11
      As greater the effective nuclear charge, more is the attraction of nucleus towards electrons hence higher will be the electron affinity. Thus, \[N{{a}^{+}}\] has higher E.A. than \[{{F}^{-}}\] and other two. Similarly, \[{{F}^{-}}\] has higher E.A than\[{{O}^{-}}\] and \[O\]. Among \[{{O}^{-}}\] and \[O\], \[{{O}^{-}}\] has lower E.A. value than \[O\] due to its greater size. As greater the atomic radius of the atom less will be the attraction of the nucleus to electron added and hence, lower will be the value of E.A. Thus, the correct order of electron affinity is \[{{O}^{-}}<O<F<N{{a}^{+}}\]


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