chemical elements which tend to localize their valence electrons rather than forming a metallic material

Nonmetals or non-metals are chemical elements which do not have the properties of a metal.

They gain electrons when reacting with a metal. They are generally not lustrous and are bad conductors of heat and electricity. Some are gases including: hydrogen, helium, oxygen, nitrogen, fluorine, neon or radon and others. An example of a solid that is a nonmetal is sulfur. It is yellow and not shiny at all. An example of a liquid that is a nonmetal is bromine. It is red. A non-metal is a good insulator for heat and cold. Usually, gases or brittle solids are non-metals.

Elements on the periodic table can be classified as metal, semimetal, or non-metal. Five times more elements are metals than nonmetals. However, nonmetals are abundant and important. Two of the nonmetals—hydrogen and helium—make up over 99 per cent of the observable Universe, and one—oxygen—makes up close to half of the Earth's crust, oceans and atmosphere. Living organisms are also composed almost entirely of nonmetals, and nonmetals form many more compounds than metals.