NEET AIPMT SOLVED PAPER 1998

  • question_answer
                    Bohr radius for the hydrogen atom (n = 1) is approximately 0.530 \[\overset{\text{o}}{\mathop{\text{A}}}\,\]. The radius for the first excited state (n = 2) orbit is (in \[\overset{\text{o}}{\mathop{\text{A}}}\,\]):

    A)                                                                                                                                                                                                                 0.13

    B)                 1.06       

    C)                            4.77       

    D)                                            2.12

    Correct Answer: D

    Solution :

                    \[r\propto \,n_{1}^{2}\,{{Z}^{2}}\]                 where n = number of orbit                 Z = Atomic number                 \[\because \]     \[{{r}_{1}}\propto n_{1}^{2}\]                 \[{{r}_{2}}\propto \,n_{2}^{2}\,(Z=1\,for\,H-atom)\]                 \[So,\frac{{{r}_{1}}}{{{r}_{2}}}=\frac{n_{1}^{2}}{n_{2}^{2}}\]                 \[\frac{0.530}{{{r}_{2}}}=\frac{{{1}^{2}}}{{{2}^{2}}}\]                 \[\therefore {{r}_{2}}=0.530\times 4=2.120\,{\AA}\]


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