Which orbital does not fill before a 4s in a multielectron atom?
A)2s
B)2p
C)3s
D)3p
E)3d

Question

Quizplus · Accepted Answer

The 3d orbital does not fill before a 4s orbital in a multielectron atom. This is due to the fact that the 3d orbital has a higher energy than the 4s orbital in a neutral atom, but as electrons are added to the atom, the repulsion between the electrons causes the energy of the 4s orbital to rise more rapidly than the energy of the 3d orbital, causing the 4s orbital to fill before the 3d orbital.

Which Orbital Does Not Fill Before a 4s in a Multielectron