Explanation:
Noble gas configuration is defined as the configuration which contains completely filled orbitals.
For example, oxygen atom when gain two electrons then it forms oxygen ion ([tex]O^{2-}[/tex]).
Atomic number of oxygen atom is 8 and so, its number of electrons will also be 8. But when it gain two electrons then it has total 10 electrons. Hence, electronic configuration of [tex]O^{2-}[/tex] is as follows.
[tex]1s^{2}2s^{2}2p^{6}[/tex]
Since, there are completely filled orbitals in an [tex]O^{2-}[/tex] ions. Therefore, it means this ion has a noble-gas configuration.
Thus, we can conclude that any specie which shows completely filled orbitals will have noble-gas configuration.
