JCECE Engineering JCECE Engineering Solved Paper-2004

  • question_answer
    The energy of last electron of Li will be:

    A) \[-30.6\,\,eV\]                 

    B) \[-13.6\,\,eV\]

    C) \[-24.6\,\,eV\]                 

    D)  \[-28.6\,\,eV\]

    Correct Answer: A

    Solution :

    Key Idea: Energy of electron\[=\frac{-13.6{{Z}^{2}}}{{{n}^{2}}}eV\] where \[Z=\]atomic number of element, for\[Li=3\] \[n=\]number of orbit, for last\[{{e}^{-}}\]of\[Li,\,\,n=2\] \[\therefore \]Energy of last electron of\[Li\]                 \[=\frac{-13.6\times {{(3)}^{2}}}{{{(2)}^{2}}}=\frac{-13\times 9}{4}\]                 \[=-30.6\,\,eV\]


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