Question

organize the sublevels from lowest to highest energy. (fills first) (fills last) move! 3d 4p 3s 1s 2s 4s 2p 4d 5s 3p low high

Explanation:

Step1: Recall the Aufbau principle

Electrons fill sub - levels in order of increasing energy. The order of filling is determined by the (n + l) rule, where n is the principal quantum number and l is the angular momentum quantum number (s: l = 0, p: l = 1, d: l = 2).

Step2: Analyze each sub - level

1s has n = 1 and l=0, (n + l)=1; 2s has n = 2 and l = 0, (n + l)=2; 2p has n = 2 and l = 1, (n + l)=3; 3s has n = 3 and l = 0, (n + l)=3, but since n is larger than 2, it has higher energy than 2p; 3p has n = 3 and l = 1, (n + l)=4; 4s has n = 4 and l = 0, (n + l)=4, but due to shielding effects, it has lower energy than 3d; 3d has n = 3 and l = 2, (n + l)=5; 4p has n = 4 and l = 1, (n + l)=5, but higher n than 3d makes it higher in energy; 5s has n = 5 and l = 0, (n + l)=5, higher n than 4p and 3d makes it higher in energy; 4d has n = 4 and l = 2, (n + l)=6.

Step3: Arrange in order

1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d

Answer:

1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d