AIIMS AIIMS Solved Paper-2004

  • question_answer
         In the basic \[CsCl\] crystal structure, \[C{{s}^{+}}\]and \[C{{l}^{-}}\] ions are arranged in a bcc configuration as shown in the figure. The net electrostatic force exerted by the eight Cs+ ions on the\[C{{l}^{-}}\] ion is:

    A) \[\frac{1}{4\pi {{\varepsilon }_{0}}}\frac{4{{e}^{2}}}{3{{a}^{2}}}\]

    B)                       \[\frac{1}{4\pi {{\varepsilon }_{0}}}\frac{16{{e}^{2}}}{3{{a}^{2}}}\]           

    C)       \[\frac{1}{4\pi {{\varepsilon }_{0}}}\frac{32{{e}^{2}}}{3{{a}^{2}}}\]           

    D)       zero

    Correct Answer: D

    Solution :

                    Key Idea: The given crystal structure is a body centered cubic structure. The electrostatic force. \[F=\frac{1}{4\pi {{\varepsilon }_{0}}}\frac{{{q}_{1}}{{q}_{2}}}{{{r}^{2}}}\] due to one \[C{{s}^{+}}\] ion is balanced by diagonally opposite \[C{{s}^{+}}\] ion. Hence, net electrostatic force on \[C{{l}^{-}}\] ion due to eight \[C{{s}^{+}}\] ions is zero.


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