Some elements have a marked mixture of metallic and nonmetallic properties which of these borderline cases are counted as nonmetals can vary depending on the classification criteria. While the term non-metallic dates from at least 1566, there is no widely agreed precise definition of a nonmetal.
Nearly all nonmetals have individual uses in medicine and pharmaceuticals lighting and lasers and household items. Living organisms are composed almost entirely of the nonmetals hydrogen, oxygen, carbon, and nitrogen. Most nonmetals have biological, technological or domestic roles or uses. Five nonmetallic elements, hydrogen, carbon, nitrogen, oxygen and silicon, largely make up the Earth's crust, atmosphere, oceans and biosphere. Two nonmetals, hydrogen and helium, make up about 99% of ordinary matter in the observable universe by mass. Nonmetal atoms are moderately to highly electronegative they tend to attract electrons in chemical reactions and to form acidic compounds. The electrons in metals are generally free moving and this is why metals are good conductors and most are easily flattened into sheets and drawn into wires. With some exceptions, those in nonmetals are fixed in place, resulting in nonmetals usually being poor conductors of heat and electricity and brittle or crumbly when solid. The electrons in nonmetals behave differently from those in metals.
In chemistry, a nonmetal is a chemical element that generally lacks a predominance of metallic properties they range from colorless gases (like hydrogen) to shiny and high melting point solids (like boron).
#Periodic table metals and nonmetals full#
Hydrogen is usually in group 1 (per the below full table) but can be in group 17 (per the above extract).
There is no precise definition of a nonmetal which elements are counted as such varies. Extract of periodic table showing how often each element is classified as a nonmetal:ġ4 effectively always 3 frequently 6 sometimes ( metalloids)
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