The table shows the electronic structures of some noble gases. All the noble gases have complete outer shells:
When elements react, their atoms complete their outer shells by losing, gaining, or sharing electrons. Atoms of group 0 elements already have stable arrangements of electrons. This means that they have no tendency to lose, gain, or share electrons. This is why the noble gases are unreactive. It also explains why atoms of group 0 elements do not share electrons to form molecules.