Nonmetal, or non-metal, is a term used in chemistry when classifying the chemical elements. On the basis of their general physical and chemical properties, every element in the periodic table can be termed either a metal or a nonmetal. (A few elements with intermediate properties are referred to as metalloids).

The elements generally regarded as nonmetals are:

  • In Group 1: hydrogen (H) (The only nonmetal in this group)
  • In Group 14: carbon (C) (Again, the only nonmetal in this group)
  • In Group 15: (the pnictogens): nitrogen (N), phosphorus (P)
  • In Group 16: (the chalcogens): oxygen (O), sulfur (S), selenium (Se)
  • In Group 17: (the halogens): fluorine (F), chlorine (Cl), bromine (Br), iodine (I)
  • All elements (with the possible exception of ununoctium) in Group 18 – the noble gases

There is no rigorous definition for the term "nonmetal" – it covers a general spectrum of behaviour. Common properties considered characteristic of a nonmetal include:

  • poor conductors of heat and electricity when compared to metals
  • they form acidic oxides (whereas metals generally form basic oxides)
  • in solid form, they are dull and brittle, rather than metals which are lustrous, ductile or malleable
  • usually have lower densities than metals
  • they have significantly lower melting points and boiling points than metals (with the exception of carbon)
  • non-metals have high electronegativity

Only eighteen elements in the periodic table are generally considered nonmetals, compared to over eighty metals, but nonmetals make up most of the crust, atmosphere and oceans of the earth. Bulk tissues of living organisms are composed almost entirely of nonmetals. Most nonmetals are monatomic noble gases or form diatomic molecules in their elemental state, unlike metals which (in their elemental state) do not form molecules at all.

Read more about Nonmetal:  Metallic Allotropes

Other articles related to "nonmetal, nonmetals":

Period 2 Element - Elements
... Alkali metal 2s1 4 Be Beryllium Alkaline earth metal 2s2 5 B Boron Metalloid 2s2 2p1 6 C Carbon Nonmetal 2s2 2p2 7 N Nitrogen Nonmetal 2s2 2p3 8 O Oxygen Nonmetal 2s2 2p4 ...
Elements Less Commonly Recognized As Metalloids - Astatine
... Astatine may be a nonmetal or a metalloid ... It is ordinarily classified as a nonmetal, but has some 'marked' metallic properties ... In 1949 it was called the most noble (difficult to reduce) nonmetal as well as being a relatively noble (difficult to oxidize) metal ...
Chemistry - Ionic Bonding
... The most common type of ionic bonding is seen in compounds of metals and nonmetals (except noble gases, which rarely form chemical compounds) ... metal is combined with a highly electronegative nonmetal, the extra electrons from the metal atoms are transferred to the electron-deficient nonmetal ... This reaction produces metal cations and nonmetal anions, which are attracted to each other to form a salt ...
Nonmetal - Metallic Allotropes
... Among the nonmetals, many possess metallic allotropes under high pressure, while some metals may exist in nonmetallic allotropes Element Period Group ... Carbon 14 ... other nonmetal A metallic allotrope of carbon has been hypothesized to occur at 1.1 TPa ... Nitrogen 15 ... other nonmetal There has been some theoretical consideration of a high-pressure metallic allotrope ...
Pyrophoricity - Pyrophoric Materials - Solids
... Alkylated metal alkoxides or nonmetal halides (diethylethoxyaluminium, dichloro(methyl)silane) Alkali metals (lithium, sodium, potassium, rubidium, caesium) (Including the alloy NaK ... as Raney nickel (especially hazardous because of the adsorbed hydrogen) Metal hydrides or nonmetal hydrides (germane, diborane, sodium hydride ... fully alkylated derivatives of metal and nonmetal hydrides (diethylaluminium hydride, trimethylaluminium, triethylaluminium, butyllithium), with a few exceptions (i.e ...