Ncert Exercises & Solutions

The electronic configurations of the elements A, B, and C are given below.

$A = 1 s^{2} 2 s^{2} 2 p^{6}$
$B = 1 s^{2} 2 s^{2} 2 p^{6} 3 s^{2} 3 p^{3}$
$C = 1 s^{2} 2 s^{2} 2 p^{6} 3 s^{2} 3 p^{5}$

The stable form of A may be represented by the formula:

1.	A	2.	A₂
3.	A₃	4.	A₄

HINT: Noble gas does not form diatomic molecule.

Explanation:

STEP 1 :

The given electronic configuration shows that A represents noble gas because its octet is complete.

A is neon which has 10 atomic number. Noble gas is non reactive.

STEP 2:

So, A cannot form $A_{2}, A_{3} and A_{4}$ . Hence, Stable form of A is A.