Question

The quantum number of four electrons are given below:

1. n = 4, l = 2, m₁ = - 2, m_s = `- 1/2`
2. n = 3, l = 2, m₁ = 1, m_s = `+ 1/2`
3. n = 4, l = 1, m₁ = 0, m_s = `+ 1/2`
4. n = 3, l = 1, m₁ = 1, m_s = `- 1/2`

The correct order of their increasing energies will be:

Options

• IV < III < II < I 

• I < II < III < IV 

• IV < II < III < I

• I < III < II < IV

Answer 1

IV < II < III < I

Explanation:

According to the selection rule, the energy level is inversely proportional to the value of (n + l), therefore if two subshells have the same value of (n + l), the subshell with the lower value of n will have a lower level.

	n	l	n + l
I	4	2	4 + 2 = 6
II	3	2	3 + 2 = 5
III	4	1	4 + 1 = 5
IV	3	1	3 + 1 = 4

Therefore the correct order of their increasing energies will be IV < II < III < I.