Question

Choose from the following:; 6C, 8O, 10Ne, 11Na, 14Si; (i) Elements that should be in the same period.; (ii) Elements that should be in the same group. State reason for your selection in each case(All India - 2012)

Answer 1

Elements that should be in the same period are

     - Carbon(C - 6), Oxygen(O - 8) and Neon(Ne - 10) belong to second period. In all these elements differentiating electron enters 2nd energy level. Hence, they are from second period.

      - Sodium(Na - 11) and Silicon (Si - 14) belong to third period. The differentiating electron enters 3rd energy level. Hence, they belong to third period.

Elements that should be in the same group are

      - Carbon and Silicon belong to group 14 as both of them have general electronic configuration of  $ns^{2}np^{2}$.