Question

Identify the noble gas element which does not belongs to p-block.

• A. Krypton (Kr)
• B. Helium (He)
• C. Neon(Ne)
• D. Argon (Ar)

Answer 1

The correct option is B Helium (He)

The electronic configurations of the given elements are:
He - $1s^2$
Kr - $1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}3d^{10}4p^6$
Ne - $1s^{2}2s^{2}2p^6$
Ar - $1s^{2}2s^{2}2p^{6}3s^{2}3p^6$

Helium belongs to the s- block because its last electron goes into the s-subshell. It also is a noble gas element because it has completely filled outermost orbit which makes it highly inert or unreactive to other elements.
Rest all the elements belong to p-subshell as they have their last electrons in the p-subshell.