Question

Which element would be inert in nature? 

(a) Element with 2 electrons

(b) Element with 9 electrons

(c) Element with 12 electrons

(d) Element with 20 electrons​

Answer 1

The correct option is a.

• The element which has filled the valance shell is inert.
• The electronic configuration of an element with 2 electrons is $1s^2$. So, it has a filled valance shell and it is inert.
• The electronic configuration of an element with 9 electrons is $1s^22s^22p^5$. So, it does not contain a filled valance shell and it is not inert.
• The electronic configuration of an element with 12 electrons is $1s^22s^22p^63s^2$. So, it does not contain a filled 3p orbital and it is not inert.
• The electronic configuration of an element with 20 electrons is $1s^22s^22p^63s^23p^64s^2$. So, it does not contain a filled 3d orbital and it is not inert.