Generally, atoms react and complete their octet to become stable. However, noble gases already have a complete octet. They do not need to interact with other atoms in order to get stable. This makes noble gases unreactive. This low reactivity can be explained using the following factors.
Octet and Duplet rule
The preference of atoms to have eight electrons in the outermost electronic shells is called as octet rule. This octet number of electrons is completed either by gaining or losing electrons.
Atoms do so by reacting chemically with other atoms or ions and so are known as Reactive. This, however, does not happen in case of noble gases. These atoms already have a stable electronic state making them unable to react or respond to chemical changes around them.
Another preference of smaller atoms to have two electrons in the outermost electronic shell is called as duplet rule. This rule is only followed by atoms with fewer electrons like Hydrogen (H), Helium (He), and Lithium (Li). Sometimes, this Duplet rule is also known as the duet rule.
Position in the periodic table
Noble gases lie in VIII A, also called the zero group of the periodic table. This last group is known for the complete number of electrons in valence shells i.e. 8 electrons (Octet). They are also known as inert gases for being inert to chemical changes or reactions.
Electronic configuration of Noble gases
Noble gases, being inert, have completely filled electronic shells making their electronic configurations stable or standard.
He = [He]2 = 1s2
Ne = [Ne]10 = 1s2, 2s2, 2p6
Ar = [Ar]18 = 1s2, 2s2, 2p6, 3s2, 3p6
Kr = [Kr]36 = 1s2, 2s2, 2p6, 3s2, 3p6,3d10, 4s2, 4p6
Xe = [Xe]54 = 1s2, 2s2, 2p6, 3s2, 3p6, 3d10, 4s2, 4p6,4d10, 5s2, 5p6
Rn = [Rn]86 = 1s2, 2s2, 2p6, 3s2, 3p6, 3d10, 4s2, 4p6,4d10, 4f14, 5s2, 5p6, 5d10, 6s2, 6p6
Normally, the noble gases compounds are highly unstable. They can be stored under specified conditions e.g. 40K temperature and in Argon matrix to make some exceptional compounds.
Reactive exceptions in Noble gases
Despite such unreactivity, some compounds of noble gases have been found.
XeF2, XeF4, XeF6, XeCl, XeCl2, KrF2, HArF, RnF2
XeO2, XeO3, XeO4, RnO3
XeOF2, XeOF4, XeO2F2, XeO3F2, XeO2F4
Neon and Helium compounds
Ne+, (NeAr)+, (NeH)+, (HeNe)+, Na2He