Question

of the following, which sublevel is filled last?
answer:
a 3d
b 4s
c 4p
d 4d
e 5s

Explanation:

According to the Aufbau principle, electrons fill orbitals in order of increasing energy. The energy order of the given sublevels is \(4s < 3d < 4p < 5s < 4d\). So, among the options, the \(4d\) sublevel has the highest energy and is filled last.

Answer:

D. \(4d\)