How many sublevels, orbitals and electrons can be present in the M-shell of an atom?

 

In an atom, electrons are located in different energy levels outside the nucleus. In the case of M - shell or energy level, n = 3. These shells or energy levels are divided into sub-energy levels. The sub-energy level is denoted by "l". The value of "l" ranges from zero (0) to (n- 1).

The sub-energy levels are again divided into different orbitals. In different orbitals, the electrons are arranged in three dimensions. This is called the magnetic quantum number (m). The value of m ranges from zero (0) to ± l.

For M - shell, if n = 3, then l = 0,1,2. Then there will be three sub-energy levels - 3s, 3p and 3d.

Then, for l = 0, m = 0. That is, there will be a 3s orbital.

For l = 1, m = 0, ±1. That is, there will be three 3p orbitals.

For l = 2, m = 0, ±1, ±2. That is, there will be five 3d orbitals.

That is, there are nine orbitals in the M-shell, one 3s, three 3p, and five 3d.

Again, we know from the spin quantum number (s), that an orbital can hold a maximum of two electrons.

So, the number of electrons in the M-shell is

= 9 x 2 = 18.

Therefore, the M-shell can hold three sublevels, nine orbitals, and eighteen electrons.

(If l = 0, it is the s-sublevel, if l = 1, it is the p-sublevel, if l = 2, it is the d-sublevel, if l = 3, it is the f-sublevel.)