Question

which sublevel below would be filled last by electrons?
o 1s
o 4p
o 5d
o 5s

Explanation:

Electrons fill sub - levels according to the Aufbau principle, which states that lower energy sub - levels are filled first. The order of filling is based on the (n + l) rule (where n is the principal quantum number and l is the angular momentum quantum number). For 1s, (n + l)=1 + 0 = 1; for 4p, (n + l)=4+1 = 5; for 5d, (n + l)=5 + 2=7; for 5s, (n + l)=5+0 = 5. Among these, the 5d sub - level has the highest (n + l) value and is filled last.

Answer:

C. 5d