Why can scientists ignore the forces of attraction between particles in a gas under ordinary conditions

The forces of attraction between particles in their gaseous state seems to be nonexistential.
therefore scientist would care less. however another state after gas which is plasma has a lesser force of attraction than the gaseous state.

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.