He can repeat his experiment multiple times, and ask a friend to repeat it as well to see if they get the same answer.
It has to be A i hope this helped
The aufbau principle, from the German Aufbauprinzip (building-up principle), also called the aufbau rule, states that in the ground state of an atom or ion, electrons fill atomic orbitals of the lowest available energy levels before occupying higher levels.
Answer:
3
Explanation:
third answer might be right
