For n+l = 4, the following are the possibilities:
- n = 4, l = 0 which is 4s having 1 orbital in which 2 electrons are present
- n = 3, l = 1 which is 3p having 3 orbitals in which 6 elctrons are present (2 in each).
- n = 2, l = 2 is not possible becuase l = n-1 always
So in total there are 4 orbitals and 8 electrons.