Question

The third period contains only eight element even through the electron capacity of the third shell is 18

Answer 1

This is due to energy considerations, after the 3p orbital, 4s orbital is filled causing the maximum no. of electrons accomodated in the 3rd orbital to be 8 till the 4s orbital is fully filled.

Answer 2

Answer:

Explanation:

(i) Period 3 of the periodic table consists of elements

whose atom has three shells occupied by electrons.

(ii) As per the electron holding capacity of shells,

2 elements are present in the first period, and

8 elements in the second period.

(iii) The third period also contain only eight elements

due to the law of electron octet and also electrons

will fill orbitals in increasing order of energy, i.e.

the lowest energy orbital first.