RAJASTHAN PMT Rajasthan - PMT Solved Paper-2003

  • question_answer
    The energy of a hydrogen-like atom in its ground state is -54.4 eV. It may be

    A)  hydrogen          

    B)         deuterium

    C)  helium                

    D)         lithium

    Correct Answer: C

    Solution :

    Energy of H-like atoms,          \[{{E}_{n}}=-\frac{{{Z}^{2}}Rhc}{{{n}^{2}}}=-\frac{{{Z}^{2}}\times 13.6\,eV}{{{n}^{2}}}\] For ground state \[n=1\] \[{{E}_{1}}=-54.4eV\](given) \[\therefore \]          \[-54.4\,eV=\frac{{{Z}^{2}}\times 13.6}{{{(1)}^{2}}}eV\] \[\Rightarrow \]               \[{{Z}^{2}}=4\] or            \[Z=2\]                                 \[Z=2\] is for helium.


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