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Which of the sets below are not in the order of lowest energy to highest energy?

A. [tex]3s, 4p, 4s, 3p[/tex]
B. [tex]2s, 2p, 3s, 3p[/tex]
C. [tex]3p, 4s, 3d, 4p[/tex]
D. [tex]3s, 3p, 4s, 3d[/tex]

Answer :

To determine which set of electron orbitals is not in order of lowest energy to highest energy, we need to refer to the order in which electron orbitals are filled, known as the Aufbau principle. This order is based on the energy levels of the orbitals. For the orbitals we are considering, the general order from lowest to highest energy is:

1. 1s
2. 2s
3. 2p
4. 3s
5. 3p
6. 4s
7. 3d
8. 4p

Using this order, let's examine each set of electron orbitals provided in the question:

1. Set 1: 3s, 4p, 4s, 3p
- In terms of energy: 3s (4), 4p (8), 4s (6), 3p (5)
- This set is not in the correct order of increasing energy. It should be 3s, 3p, 4s, 4p.

2. Set 2: 2s, 2p, 3s, 3p
- In terms of energy: 2s (2), 2p (3), 3s (4), 3p (5)
- This set is in the correct order of increasing energy.

3. Set 3: 3p, 4s, 3d, 4p
- In terms of energy: 3p (5), 4s (6), 3d (7), 4p (8)
- This set is in the correct order of increasing energy.

4. Set 4: 3s, 3p, 4s, 3d
- In terms of energy: 3s (4), 3p (5), 4s (6), 3d (7)
- This set is in the correct order of increasing energy.

Given the examination above, only Set 1 is not in the order of lowest to highest energy based on the levels stated in the Aufbau principle.

Therefore, the set that is not ordered correctly from lowest energy to highest energy is:

- Set 1: 3s, 4p, 4s, 3p

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