Question

As per Moeller chart, the correct ascending order of their energies of the following orbitals is

• A. 3s <3p <4s <3d
• B. 3s <3p <4s <3d
• C. 3s<4s <3p < 3d
• D. 3s<3d <4s <3p

Answer 1

The Correct Option is A

✅ Correct answer: 3s < 3p < 4s < 3d

Explanation: 
According to the Moeller chart (also known as the Aufbau principle), electrons fill atomic orbitals in the order of increasing energy. The energy order of orbitals is determined using the n + l rule, where:
- n is the principal quantum number
- l is the azimuthal quantum number

If two orbitals have the same n + l value, the orbital with the lower n value has lower energy.

Using this rule:
- 3s (n + l = 3 + 0 = 3)
- 3p (n + l = 3 + 1 = 4)
- 4s (n + l = 4 + 0 = 4)
- 3d (n + l = 3 + 2 = 5)

So the correct order is:
3s < 3p < 4s < 3d

Answer 2

The correct answer is 3s < 3p < 4s < 3d. According to the Moeller chart, the energy levels of orbitals follow a specific order. For the orbitals in question, the energy order is: - 3s has the lowest energy, - 3p comes next, - 4s has lower energy than 3d, - 3d has the highest energy among these orbitals. Thus, the correct ascending order of their energies is 3s < 3p < 4s < 3d.