What is the ionic composition and osmolarity of "physiological saline" - the intravenous fluid drip you receive at a hospital?

The physiological saline is made from 0.9% NaCl solution. That means the ionic composition of the solution would be Na and Cl with 308 mOsmol/L. The osmolality of the solution is near blood osmolality so it can be called isotonic. The isotonic solution will not induce osmosis so they will not hurt the cells. Saline ion also easily removed so it will be safe to administer a high amount of the solution, unlike solution with dangerous ion like potassium. That is why the physiological saline is used when fluid resuscitation.

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.