How many moles of nitrogen are contained in 18.65 l at stp?

We can use the ideal gas law equation to find the number of moles of nitrogen at STP
PV = nRT
Where
P - standard pressure - 1 atm
V - 18.65 L
n - number of moles
R - universal gas constant - 0.0821 L.atm/mol.K
T - standard temperature -273 K
Substituting the values in the equation
1 atm x 18.65 L = n x 0.0821 L.atm/mol.K x 273 K
n = 0.832 mol
There are 0.832 mol of Nitrogen gas in the container

The problem here is that according to aufbau principle before 3d orbital 4s subshell comes.after filling 3p orbital with electrons you have 4 electrons left, you place two in 4s with opposite spin and the other two in 3d in any of its two orbitals of total five orbitals with the same spin.