CET Karnataka Medical CET - Karnataka Medical Solved Paper-2004

  • question_answer
    Which state of triply ionised Beryllium (\[B{{e}^{+++}}\]) has the same orbital radius as that of the ground state of hydrogen?

    A)  n = 3

    B)  n = 4

    C)  n = 1

    D)  n = 2

    Correct Answer: D

    Solution :

    Radius of orbit of electron in nth excited state of hydrogen \[r=\frac{{{\varepsilon }_{0}}{{h}^{2}}{{n}^{2}}}{\pi mZ{{e}^{2}}}\] \[\therefore \] \[r\propto \frac{{{n}^{2}}}{Z}\] \[\therefore \] \[\frac{{{r}_{1}}}{{{r}_{2}}}=\frac{n_{1}^{2}}{n_{2}^{2}}\times \frac{{{Z}_{2}}}{{{Z}_{1}}}\] But \[{{r}_{1}}={{r}_{2}}\] So, \[n_{2}^{2}=n_{1}^{2}\times \frac{{{Z}_{2}}}{{{Z}_{1}}}\] Here : \[{{n}_{1}}=1\](ground state of hydrogen), \[{{Z}_{1}}=1\](atomic number of hydrogen), \[{{Z}_{2}}=4\](atomic number of Beryllium) \[\therefore \] \[n_{2}^{2}={{(1)}^{2}}\times \frac{4}{1}\] or \[n_{2}^{2}=4\] or \[n_{2}^{{}}=2\]


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