The maximum number of electrons present in the main energy level in which the ‘g’ subshell appears for the first time is

The maximum number of electrons present in the main energy level in which the ‘g’ subshell appears for the first time is 50.

The value of ‘l’ for the g subshell is 4. The principal quantum number of the g subshell is 5 (l= n-1). So, the maximum number of electrons that can be accommodated in 5^th orbit is 2x5² = 50 electrons.

Orbitals should be filled before filling of 5g subshell are $1s,2s,2p,3s,3p,4s,3d,4p,5s,4d,5p,6s,4f,5d,6p,7s,5f,6d,7s,5f,6d,7p,8s,5g.$

So, the atomic number will be 121.