BCECE Engineering BCECE Engineering Solved Paper-2009

  • question_answer
    Which of the following pairs of atomic numbers represents s-block elements?

    A)  7, 15     

    B)         6, 12     

    C)         9, 17                     

    D)         3, 11

    Correct Answer: D

    Solution :

    s-block elements contain either 1 or 2 electrons in their outer most shell. \[3=1{{s}^{2}},2{{s}^{1}}\] \[11=1{{s}^{2}},2{{s}^{2}},2{{p}^{6}},3{{s}^{1}}\] From the above electronic configuration, it is clear that elements having atomic number 3 and 11 belong to s-block. Since, both contains one electron in outer most shell, these belong to alkali metals.


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