Question

How many orbitals are there in the third shell (n = 3)?

Answer 1

Hint: In order to find the number of orbitals present in the third electron shell, we must first know what an electron shell is. Electron shell is an orbit which is followed by the electrons around the nucleus of an atom.

Complete step by step answer:
- Let us now see in detail about electron shells. Electron shell is an orbit which is followed by the electrons around the nucleus of an atom.
- The shell which is nearest to the nucleus is the first shell which is labelled as K shell. The Second shell is little far away from the nucleus and is labelled as the L shell. The third shell is labelled as the M shell and the fourth shell Is labelled as the N shell. This naming is done on the basis of the principal quantum number. That is the shell corresponding to the principal quantum number n = 1,2,3,4 is labelled alphabetically as K, L, M, N respectively.
- Each shell will be having one or more subshells. The K shell (n=1) will be having only one subshell, i.e., 1s subshell. L shell will be having two subshells, i.e., 2s and 2p. M shell (n=3) will be having three sub shells i.e., 3s, 3p and 3d. The N shell (n=4) will be having four subshells i.e., 4s, 4p, 4d and 4f subshells.
- Now let us come to the question given:
The third shell is the M shell which will be having three subshells namely 3s, 3p and 3d.
The 3s subshell will be having only 1 orbital.
The 3p subshell will be having 3 orbitals.
The 3d subshell will be having 5 orbitals.
On adding all the orbitals of 3s, 3p and 3d we get a total of 9 orbitals.
Therefore, there are 9 orbitals in the third shell.

Note: We have to remember that the filling of the electrons in the orbitals takes place on the basis of three rules, they are:
- Hund’s Rule:
Every orbital in a subshell should be singly filled before any of the orbitals are doubly filled. Each singly filled orbital should have the same spin.
- Pauli’s exclusion principle:
No two electrons in an atom can have all four quantum numbers identical.
- Aufbau principle:
The filling of the electrons in the orbitals takes place in the increasing order of the energies of the orbitals.