Editing Nonmetal (section)

==Definition and applicable elements==
:''Unless otherwise noted, this article describes the stable form of an element at [[standard temperature and pressure]] (STP).''{{efn|The most stable forms are: diatomic [[hydrogen]] H<sub>2</sub>; [[allotropes of boron#β-rhombohedral boron|β-rhombohedral boron]]; [[graphite]] for [[carbon]]; diatomic [[nitrogen]] N<sub>2</sub>; diatomic [[oxygen]] O<sub>2</sub>; tetrahedral [[silicon]]; [[black phosphorus]]; orthorhombic [[sulfur]] S<sub>8</sub>; [[germanium#Characteristics|α-germanium]]; gray [[arsenic]]; gray [[selenium]]; gray [[antimony]]; gray [[tellurium]]; and diatomic [[iodine]] I<sub>2</sub>. All other nonmetallic elements have only one stable form at [[standard temperature and pressure|STP]].<ref>[[#Wismer|Wismer 1997, p. 72]]: H, He, C, N, O, F, Ne, S, Cl, Ar, As, Se, Br, Kr, Sb, I, Xe; [[#Powell|Powell 1974, pp. 174, 182]]: P, Te; [[#Greenwood|Greenwood & Earnshaw 2002, p. 143]]: B; [[#Field|Field 1979, p. 403]]: Si, Ge; [[#Addison|Addison 1964, p. 120]]: Rn</ref>}}
[[File:Arsen 1a.jpg|thumb|While [[arsenic]] (here sealed in a container to prevent [[tarnishing]]) has a shiny appearance and is a reasonable conductor of heat and electricity, it is soft and brittle and its chemistry is predominately nonmetallic.<ref>[[#Pascoe|Pascoe 1982, p. 3]]{{Broken anchor|date=2024-05-31|bot=User:Cewbot/log/20201008/configuration|target_link=#Pascoe|reason= }}</ref>|alt=Two dull silver clusters of crystalline shards.]]

Nonmetallic [[chemical elements]] are often broadly defined as those that mostly lack properties commonly associated with metals—namely shininess, pliability, good thermal and electrical conductivity (due to their  [[Nonmetal#Structure, quantum mechanics and band structure|band structure]]), and a general capacity to form basic oxides.<ref>[[#MD|Malone & Dolter 2010, pp. 110–111]]</ref><ref name="Porterfield"/> There is no widely accepted precise definition in terms of these properties;<ref>[[#Godovikov|Godovikov & Nenasheva 2020, p. 4]]; [[#Morley|Morely & Muir 1892, p. 241]]</ref> any list of nonmetals is open to debate and revision.<ref name="Larrañaga">[[#Larrañaga|Larrañaga, Lewis & Lewis 2016, p. 988]]</ref>

Fourteen elements are almost always recognized as nonmetals:<ref name="Larrañaga"/><ref name="Steudel">[[#Steudel|Steudel 2020, p. 43]]: Steudel's monograph is an updated translation of the fifth German edition of 2013, incorporating the literature up to Spring 2019.</ref>
{{hlist | indent=1 | [[Hydrogen]] | [[Nitrogen]] | [[Oxygen]] | [[Sulfur]] }}
{{hlist | indent=1 | [[Fluorine]] | [[Chlorine]] | [[Bromine]] | [[Iodine]] }}
{{hlist | indent=1 | [[Helium]] | [[Neon]] | [[Argon]] | [[Krypton]] | [[Xenon]] | [[Radon]] }}

Three more are commonly classed as nonmetals, but some sources list them as "[[metalloids]]",<ref name="Vernon2013">[[#Vernon2013|Vernon 2013]]</ref> a term which refers to elements intermediate between metals and nonmetals:<ref name="Vernon2020p220">[[#Vernon2020|Vernon 2020, p. 220]]; [[#Rochow1966|Rochow 1966, p. 4]]</ref>
{{hlist | indent=1 | [[Carbon]] | [[Phosphorus]] | [[Selenium]] }}

One or more of the six elements most commonly recognized as metalloids are sometimes instead counted as nonmetals: 
{{hlist | indent=1 | [[Boron]] | [[Silicon]] | [[Germanium]] | [[Arsenic]] | [[Antimony]] | [[Tellurium]] }}

About 15–20% of the 118 known elements<ref>[[#IUPACPT|IUPAC Periodic Table of the Elements]]</ref> are thus classified as nonmetals.{{efn|At higher temperatures and pressures the numbers of nonmetals can be called into question. For example, when germanium melts it changes from a semiconductor to a metallic conductor with an electrical conductivity similar to that of liquid mercury.<ref>[[#Berger1997|Berger 1997, pp.&nbsp;71–72]]</ref> At a high enough pressure, [[sodium]] (a metal) becomes a non-conducting [[insulator (electricity)|insulator]].<ref>[[#Gatti|Gatti, Tokatly & Rubio 2010]]</ref>}}