Question

The following Lewis diagram represents the valence electron configuration of a main-group element. If this element is in period 3, its valence electron configuration is

Answer 1

Ans. The element is Silicon (Si) and its valence shell configuration is 3s²3p².

Explanation:-   

• Rules to find the group no. of elements:

1. if elements have 1 or 2 e^- in their valence shell then,

   Group no. of the element = No. of valence e-

   example: Na has configuration 1s2 2s22p63s1

   since, it has 1 e- in its valence shell so its group no. is 1.

       if elements have more than 2 e- (3,4,5,6,7,8) in their valence shell then,

      Group no. of the element = 10 + no. of valence e-

      ex. Carbon has configuration 1s22s22p2

      since, C has 4 e- in its valence shell so, its gp. no.= 10 + 4=14

      Gp. no. of C is 14.

• Period no. of the element =  principal quantum no. (n) of the valence shell.

      value for n for C = 2

• The block of element = type of orbital recieves last e-

      last e- of C is in p orbital so, it belongs from p-block.

      Now, according to question:

      No. of valence e- in given element = 4

      Acc. to above rule (2), this element belong from group 14 

     period no. is 3          (acc. to Q.)

Group no.               13         14              15            16                17              18

Period no. 3            Al          Si               S              P                Cl               Ar

Valence shell       3s²3p¹   3s23p2    3s23p3    3s23p4        3s23p5         3s23p6

configuration

      

In above table, it is clear that Si has 4 e- in its valence shell and the last e- is in       p orbital so it is from p-block.

     So, the element is Silicon (Si)

     its valence shell configuration is 3s23p2