What is meant by electron configuration?

Answer 1

Electronic configuration is the arrangement of electrons in the respective shells of an atom when it is in its ground state,(where all of its electrons are in their respective lowest energy orbitals).

This is shown as the number of electrons in the subshells s, p d, f, g. The subshells are in energy sequence, low to high.

An example :-

Osmium full electronic configuration

1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 5s2 4d10 5p6 4f14 5d6 6s2

The filling of energy levels generally follows the aufbau principle.