Differentiate between metals and noble gases.

Halogens are very reactive because they need one electron to gain a full set of valence electrons whereas noble gases already have this one electron and are extremely unstable since they have their full octet. (8 electron set) They tend to not form chemical bonds because of this.

A) Noble gases have a full shell of valence electrons while metals have only a few valence electrons. Valence electrons are different - metals have a full shell while noble gases have less than half a shell