Nonmetal

A nonmetal is a chemical element that mostly lacks distinctive metallic properties. Seventeen elements are widely recognized as nonmetals. This article also covers six borderline elements (or metalloids), some or all of which are sometimes considered nonmetals.

Nonmetals tend to have low density and high electronegativity (the ability of an atom in a molecule to attract electrons to itself). They range from colorless gases like hydrogen to shiny solids like iodine. Nonmetals are often poor conductors of heat and electricity, and are brittle or crumbly as solids. Their oxides tend to be acidic.

The two lightest nonmetals, hydrogen and helium, together make up about 98% of the observable ordinary matter in the universe by mass. Five nonmetallic elements—hydrogen, carbon, nitrogen, oxygen, and silicon—make up the overwhelming majority of the Earth's crust, atmosphere, oceans and biosphere.

The distinct properties of nonmetallic elements allow for specific uses that metals often cannot achieve. They have essential uses in electronics, energy storage, agriculture, and chemical production. Hydrogen, oxygen, carbon, and nitrogen are essential building blocks for life.

Most nonmetallic elements were not identified until the 18th and 19th centuries. While a distinction between metals and other minerals had existed since antiquity, a basic classification of chemical elements as metallic or nonmetallic emerged only in the late 18th century. Since then about two dozen properties have been suggested as single criteria for distinguishing nonmetals from metals.