Question

An element has $2$ electrons in its $N$ shell,
(i) what is its atomic number?

Answer 1

Since the element has $2$ electrons in its $N$ shell thus, $N$ is the outermost shell. The configuration of elements having $2$ electrons in their $N$ shell can be written as shown below.

Shells	K	L	M	N
Electrons present in each shell	2	8	8	2

The configuration defines that the total number of electrons in the atom is $2+8+8+2=20$

Therefore, the atomic number of the atom must be $20$.