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NEET NEET SOLVED PAPER 2015 (C)

  • question_answer
    The species \[Ar,{{K}^{+}}\] and \[C{{a}^{2+}}\] contain the same number of electrons. In which order do their radii increase?            

    A)          \[Ar+{{K}^{+}}<C{{a}^{2+}}\]                    

    B)  \[C{{a}^{2+}}<Ar<{{K}^{+}}\]

    C)         \[C{{a}^{2+}}<{{K}^{+}}<Ar\]

    D)        \[{{K}^{+}}<Ar<C{{a}^{2+}}\]

    Correct Answer: C

    Solution :

    \[C{{a}^{2+}}\,<{{K}^{+}}\,<Ar\] \[Ar,{{K}^{+}}\] and \[C{{a}^{2+}}\] are isoelectronic i.e. with same number of electrons, 18. For isoelectronic species ionic radii decreases with increase in effective (relative) positive charge. Also \[Ar,\,K\] and \[Ca\] belong to the same period (3rd period).


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