More than nineteen isotopes of neon are known; naturally occurring neon, however, consists of a mixture of the three most stable isotopes. The other isotopes are not common because they are unstable.
Neon-20, neon-21 and neon-22 are the three stable isotopes. Ninety percent of naturally occurring neon is neon-20. As part of the noble gases family of the periodic table, neon generally does not interact with other elements; however, it sometimes reacts with fluorine.
This relatively inert gas occurs naturally in air at one part per 65,000. Trace amounts of neon occur in the Earth's crust and oceans. The gas is most notably used in signs and lights. Neon emits an intense orange color when bombarded with electrons.