What characteristic defines nonmetals?

The characteristic that defines nonmetals is that they are poor conductors of heat and electricity. Nonmetals tend to have high electronegativity, which means they attract electrons more strongly than metals. This property contributes to their inability to conduct heat and electricity effectively. Unlike metals, which have free-moving electrons that allow for the easy flow of electric current and heat, nonmetals usually have tightly bound electrons, making them ineffective in conducting these forms of energy.

This core characteristic distinguishes nonmetals from metals, as they are primarily insulators in terms of thermal and electrical conductivity. Nonmetals may also exhibit various states of matter, primarily found in gaseous or solid forms, but their conductive properties are a central defining factor.