How does n relate to the number of electrons allowed per main energy level

2n²

Explanation:

the number of electrons in energy level is given by 2n² where n is the energy level.

for n=1 the number of electron will be

2 (1) ² = 2 electrons

For n=2 the number of electrons will be 2 (2) ² = 2*4=8

For n=3 the number of electrons will be 2 (3) ² = 2*9=18

and so on.

the number of electrons can be calculated using 2n² where n is the number of shells

nth shell can in principle hold up to 2 (n²) electrons.