Question

What would be the subshell electronic configuration of sodium?

Answer 1

As we know that subshell is a subdivision of shell where electrons are found and it is separated by orbitals and labelled as s, p, d and f containing electrons as $2,6,10$ and $14$ respectively. We also know that electronic configuration is the distribution of electrons into different shells, subshells and orbitals in an atom.

Complete answer: As we know that distribution of various electrons into different shells, subshells and orbitals is what we call an electronic configuration of an atom. We also know that shell is the region or called principal quantum number, which is basically the collection of subshells and are labelled as K, L, M, N, etc.
Subshells are the collection or group of orbitals and are labelled as s, p, d and f within the same shell containing different shapes of orbitals and different number of electrons such as $2,6,10$ and $14$ respectively.
We also remember the rules to write or fill the electrons in the subshells and the s-orbital can accommodate a total of $2$ electrons, p can accommodate $6$electrons and d-orbital can accommodate $10$ electrons and so on.
Now, let us recall that according to Aufbau’s rule the orbitals will be filled as $1s,2s,2p,3s,3d..$. Similarly, sodium is the s-block element which contains $11$ electrons, so the subshell electronic configuration of sodium will be as followed:
$1{s^2}2{s^2}2{p^6}3{s^1}$

Note: Always remember that for a complete electronic configuration, the principal quantum number is written before the respective subshell. And orbitals of lowest energy subshells will be always filled first then only the electron will move to the next higher orbital which is clearly mentioned by Aufbau’s principle followed by Hund’s and Pauli’s exclusion principle.