Nonmetal: Difference between revisions

The two lightest nonmetals, hydrogen and [[helium]], together make up about 98% of the mass of the [[observable universe]]. Five nonmetallic elements—hydrogen, carbon, [[nitrogen]], [[oxygen]], and [[silicon]]—make up the bulk of Earth's [[Atmosphere of Earth|atmosphere]], [[biosphere]], [[Earth's crust|crust]] and [[ocean]]s.

Most nonmetallic elements were identified in 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 overabout thirtytwenty properties have been suggested as criteria for distinguishing nonmetals from metals.

Nonmetallic [[chemical elements]] are often described as lacking properties common to metals, namely shininess, pliability, good thermal and electrical conductivity, 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;<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> The elements included depend on the properties regarded as most representative of nonmetallic or metallic character.

About half of nonmetallic elements are gases under [[standard temperature and pressure]]; most of the rest are solids. Bromine, the only liquid, is usually topped by a layer of its reddish-brown fumes. The gaseous and liquid nonmetals have very low densities, [[melting point|melting]] and [[boiling point]]s, and are poor conductors of heat and electricity.<ref name="Kneen">[[#Kneen|Kneen, Rogers & Simpson 1972, pp. 261–264]]</ref> The solid nonmetals have low densities and low mechanical strength (often being either hard and brittle, or soft and crumbly),<ref name="ReferenceA">[[#Phillips1973Johnson1966|PhillipsJohnson 19731966, p. 74]]</ref>{{Dubious|Dubious cites|date=August 2024|reason=This is not stated in the source given. The only relevant mention of "brittle" is on p270 where nonmetallic materials such as MgO are being discussed, not the elements.}} and a wide range of electrical conductivity.{{efn|The solid nonmetals have electrical conductivity values ranging from 10⁻¹⁸ S•cm⁻¹ for sulfur<ref name="A&W"/> to 3 × 10⁴ in graphite<ref name="Jenkins">[[#Jenkins|Jenkins & Kawamura 1976, p. 88]]</ref> or 3.9 × 10⁴ for [[arsenic]];<ref>[[#Carapella|Carapella 1968, p. 30]]</ref> cf. 0.69 × 10⁴ for [[manganese]] to 63 × 10⁴ for [[silver]], both metals.<ref name="A&W">[[#Aylward|Aylward & Findlay 2008, pp. 6–12]]</ref> The conductivity of graphite (a nonmetal) and arsenic (a metalloid nonmetal) exceeds that of manganese. Such overlaps show that it can be difficult to draw a clear line between metals and nonmetals.}}

This diversity in form stems from variability in internal structures and bonding arrangements. Covalent nonmetals existing as discrete atoms like xenon, or as small molecules, such as oxygen, sulfur, and bromine, have low melting and boiling points; many are gases at room temperature, as they are held together by weak [[London dispersion force]]s acting between their atoms or molecules, although the molecules themselves have strong covalent bonds.<ref>[[#ZumDeC|Zumdahl & DeCoste 2010, pp. 455, 456, 469, A40]]; [[#Earl&W|Earl & Wilford 2021, p. 3-24]]</ref> In contrast, nonmetals that form extended structures, such as long chains of up to 1,000 selenium atoms,<ref>[[#Still|Still{{Cite 2016,journal p|last1=Corb |first1=B.W. 120]]</ref>{{Dubious|Dubiouslast2=Wei cites|datefirst2=AugustW.D. 2024|reasonlast3=ClaimAverbach is|first3=B.L. made|date=1982 in|title=Atomic amodels bookof whichamorphous citesselenium no|url=https://linkinghub.elsevier.com/retrieve/pii/0022309382900163 sources,|journal=Journal soof shouldNon-Crystalline notSolids be|language=en considered|volume=53 a|issue=1–2 reliable|pages=29–42 source|doi=10.1016/0022-3093(82)90016-3|bibcode=1982JNCS...53...29C }}</ref> sheets of carbon atoms in graphite,<ref>[[#Wiberg|Wiberg 2001, pp. 780]]</ref> or three-dimensional lattices of silicon atoms<ref>[[#Wiberg|Wiberg 2001, pp. 824, 785]]</ref> have higher melting and boiling points, and are all solids, as it takes more energy to overcome their stronger bonding.<ref>[[#Earl&W|Earl & Wilford 2021, p. 3-24]]</ref>{{Dubious|Dubious cites|date=August 2024|reason=An O-level (i.e. 16 year old) chemistry textbook is not a good source to quote. It is used several times, better sources should be used.}} Nonmetals closer to the left or bottom of the periodic table (and so closer to the metals) often have [[Delocalized electron|metallic interactions]] between their molecules, chains, or layers; this occurs in boron,<ref>[[#Siekierski|Siekierski & Burgess 2002, p. 86]]</ref> carbon,<ref>[[#Charlier|Charlier, Gonze & Michenaud 1994]]</ref> phosphorus,<ref>[[#Taniguchi|Taniguchi et al. 1984, p. 867]]: "...&nbsp;black phosphorus&nbsp;... [is] characterized by the wide valence bands with rather delocalized nature."; [[#Carmalt|Carmalt & Norman 1998, p. 7]]: "Phosphorus&nbsp;... should therefore be expected to have some metalloid properties."; [[#Du|Du et al. 2010]]: Interlayer interactions in black phosphorus, which are attributed to van der Waals-Keesom forces, are thought to contribute to the smaller band gap of the bulk material (calculated 0.19&nbsp;eV; observed 0.3&nbsp;eV) as opposed to the larger band gap of a single layer (calculated ~0.75&nbsp;eV).</ref> arsenic,<ref>[[#Wiberg|Wiberg 2001, pp. 742]]</ref> selenium,<ref>[[#Evans|Evans 1966, pp. 124–25]]</ref> antimony,<ref>[[#Wiberg|Wiberg 2001, pp. 758]]</ref> tellurium<ref>[[#Stuke|Stuke 1974, p. 178]]; [[#Donohue|Donohue 1982, pp. 386–87]]; [[#Cotton|Cotton et al. 1999, p. 501]]</ref> and iodine.<ref>[[#Steudel|Steudel 2020, p. 601]]: "...&nbsp;Considerable orbital overlap can be expected. Apparently, intermolecular multicenter bonds exist in crystalline iodine that extend throughout the layer and lead to the delocalization of electrons akin to that in metals. This explains certain physical properties of iodine: the dark color, the luster and a weak electric conductivity, which is 3400 times stronger within the layers then perpendicular to them. Crystalline iodine is thus a two-dimensional semiconductor."; [[#Segal|Segal 1989, p. 481]]: "Iodine exhibits some metallic properties&nbsp;..."</ref>

Good electrical conductivity occurs when there is [[metallic bond]]ing,<ref name="Ashcroft and Mermin">[[Ashcroft and Mermin]]</ref> however the electrons in nonmetals are often not metallic.<ref>[[ name="Ashcroft and Mermin]]<"/ref> Good electrical and thermal conductivity associated with metallic electrons is seen in carbon (as graphite, along its planes), arsenic, and antimony.{{efn|Thermal conductivity values for metals range from 6.3 W m⁻¹ K⁻¹ for [[neptunium]] to 429 for [[silver]]; cf. antimony 24.3, arsenic 50, and carbon 2000.<ref name="A&W"/> Electrical conductivity values of metals range from 0.69 S•cm⁻¹ × 10⁴ for [[manganese]] to 63 × 10⁴ for [[silver]]; cf. carbon 3 × 10⁴,<ref name="Jenkins"/> arsenic 3.9 × 10⁴ and antimony 2.3 × 10⁴.<ref name="A&W"/>}} Good thermal conductivity occurs in boron, silicon, phosphorus, and germanium;<ref name="A&W"/> such conductivity is transmitted though vibrations of the crystalline lattices of these elements.<ref>[[#Yang|Yang 2004, p. 9]]</ref> Moderate electrical conductivity is observed in the semiconductors<ref>[[#Wiberg|Wiberg 2001, pp. 416, 574, 681, 824, 895, 930]]; [[#Siekierski|Siekierski & Burgess 2002, p. 129]]</ref> boron, silicon, phosphorus, germanium, selenium, tellurium, and iodine.

Many of the nonmetallic elements are hard and brittle,{{Dubious|Dubious<ref cites|datename=August 2024|reason=Earlier ref to them being brittle is not valid}}"ReferenceA"/> where [[dislocationdislocations]] cannot readily move so they tend to undergo [[brittle fracture]] rather than deforming.<ref>{{Cite book |lastlast1=Weertman |firstfirst1=Johannes |url=https://en.wikipedia.org/wiki/Special:BookSources/978-0-19-506900-6 |title=Elementary dislocation theory |last2=Weertman |first2=Julia R. |date=1992 |publisher=Oxford University Press |isbn=978-0-19-506900-6 |location=New York}}</ref> Some do deform such as [[allotropes of phosphorus#White phosphorus |white phosphorus]] (soft as wax, pliable and can be cut with a knife, at room temperature),<ref name="Holderness 1979, p. 255">[[#Faraday|Faraday 1853, p. 42]]; [[#Holderness|Holderness & Berry 1979, p. 255]]</ref> in [[allotropes of sulfur#Amorphous sulfur|plastic sulfur]],<ref name="ReferenceE">[[#Partington1944|Partington 1944, p. 405]]</ref> and in selenium which can be drawn into wires from its molten state.<ref name="ReferenceF">[[#Regnault|Regnault 1853, p. 208]]</ref> Graphite is a standard [[solid lubricant]] where dislocations move very easily in the basal planes.<ref>{{Cite journal |last1=Scharf |first1=T. W. |last2=Prasad |first2=S. V. |date=January 2013 |title=Solid lubricants: a review |url=http://link.springer.com/10.1007/s10853-012-7038-2 |journal=Journal of Materials Science |language=en |volume=48 |issue=2 |pages=511–531 |doi=10.1007/s10853-012-7038-2 |bibcode=2013JMatS..48..511S |issn=0022-2461}}</ref>

Nonmetals have relatively high values of electronegativity, and their oxides are usually acidic. Exceptions may occur if a nonmetal is not very electronegative, or if its [[oxidation state]] is low, or both. These non-acidic oxides of nonmetals may be [[amphoteric]] (like water, H₂O<ref>[[#Eagleson1994|Eagleson 1994, 1169]]</ref>) or neutral (like [[nitrous oxide]], N₂O<ref>[[#Moody|Moody 1991, p. 365]]</ref>{{efn|While [[carbon monoxide|CO]] and [[nitrogen monoxide|NO]] are commonly referred to as being neutral, CO is a slightly acidic oxide, reacting with bases to produce formates (CO + OH⁻ → HCOO⁻);<ref>[[#House2013|House 2013, p. 427]]</ref> and in water, NO reacts with oxygen to form nitrous acid HNO₂ (4NO + O₂ + 2H₂O → 4HNO₂).<ref>[[#LewisRS|Lewis & Deen 1994, p. 568]]</ref>}}), but never basic.

They typically exhibit higher [[ionization energy|ionization energies]], [[electron affinity|electron affinities]], and [[standard electrode potential]]s than metals. Generally, the higher these values are (including electronegativity) the more nonmetallic the element tends to be.<ref>[[#Yoder|Yoder, Suydam & Snavely 1975, p. 58]]</ref> For example, the chemically very active nonmetals fluorine, chlorine, bromine, and iodine have an average electronegativity of 3.19—a figure{{efn|Electronegativity values of fluorine to iodine are: 3.98 + 3.16 + 2.96 + 2.66 &#61; 12.76/4 3.19.}} higher than that of any metallic element.

Hydrogen and helium, as well as boron through neon, have unusually small atomic radii. This phenomenon arises because the [[s shell|1s]] and [[p shell|2p subshell]]s lack inner analogues (meaning there is no zero shell and no 1p subshell), and they therefore experience less electron-electron [[Exchangeexchange interaction|exchange interactions]]s, unlike the 3p, 4p, and 5p subshells of heavier elements.<ref name="S&B">[[#Siekierski|Siekierski & Burgess 2002, pp. 24–25]]</ref>{{Dubious|date=June 2024}} As a result, ionization energies and electronegativities among these elements are higher than the [[periodic trends]] would otherwise suggest. The compact atomic radii of carbon, nitrogen, and oxygen facilitate the formation of [[double bond|double]] or [[triple bond|triple]] bonds.<ref>[[#Siekierski|Siekierski & Burgess 2002, p. 23]]</ref>

The Soviet chemist {{Interlanguage link multi|Shchukarev|2=ru|3=Щукарев, Сергей Александрович|preserve=1}} gives two more tangible examples:<ref>[[#Shchukarev|Shchukarev 1977, p. 229]]</ref>

Some nonmetallic elements exhibit [[oxidation state]]s that deviate from those predicted by the octet rule, which typically results in an oxidation state of –3 in group 15, –2 in group 16, –1 in group 17, and 0 in group 18. Examples include [[ammonia]] NH₃, [[hydrogen sulfide]] H₂S, [[hydrogen fluoride]] HF, and elemental xenon Xe. Meanwhile, the maximum possible oxidation state increases from +5 in [[pnictogen|group 15]], to +8 in [[noble gas|group 18]]. The +5 oxidation state is observable from period 2 onward, in compounds such as [[nitric acid]] HN(V)O₃ and [[phosphorus pentafluoride]] PCl₅.{{efn|Oxidation states, which denote hypothetical charges for conceptualizing electron distribution in chemical bonding, do not necessarily reflect the net charge of molecules or ions. This concept is illustrated by anions such as NO₃^&minus;, where the nitrogen atom is considered to have an oxidation state of +5 due to the distribution of electrons. However, the net charge of the ion remains −1. Such observations underscore the role of oxidation states in describing electron loss or gain within bonding contexts, distinct from indicating the actual electrical charge, particularly in covalently bonded molecules.}} [[Oxidation state#List of oxidation states of the elements|Higher oxidation states]] in later groups emerge from period 3 onwards, as seen in [[sulfur hexafluoride]] SF₆, [[iodine heptafluoride]] IF₇, and [[xenon tetroxide|xenon(VIII) tetroxide]] XeO₄. For heavier nonmetals, their larger atomic radii and lower electronegativity values enable the formation of compounds with higher oxidation numbers, supporting higher bulk [[coordination number]]s.<ref name="Cox" />

A relatively recent development involves certain compounds of heavier p-block elements, such as silicon, phosphorus, germanium, arsenic and antimony, exhibiting behaviors typically associated with [[coordination compound|transition metal complexes]]. This is linked to a small energy gap between their [[HOMO_and_LUMOHOMO and LUMO|filled and empty]] [[molecular orbitals]], which are the regions in a molecule where electrons reside and where they can be available for chemical reactions. In such compounds, this allows for unusual reactivity with small molecules like hydrogen (H₂), [[ammonia]] (NH₃), and [[ethylene]] (C₂H₄), a characteristic previously observed primarily in transition metal compounds. These reactions may open new avenues in [[catalyst|catalytic]] applications.<ref>[[#Power|Power 2010]]; [[#Crow|Crow 2013]]{{Broken anchor|date=2024-05-31|bot=User:Cewbot/log/20201008/configuration|target_link=#Crow|reason= }}; [[#Weetman|Weetman & Inoue 2018]]</ref>

| style="background-color:#FFFFFF;border-bottom:2px solid black;border-right:2px solid black;" | [[hydrogen|H]]

| style="background-color:#9BCDFD;padding-bottom:3px;" | [[helium |He]]

| style="background-color:#FC9A9B;" | [[boron |B]]

| style="background-color:#FFFFFF;" | [[carbon |C]]

| style="background-color:#FFFFFF;" | [[neon |N]]

| style="background-color:#FFFFFF;" | [[oxygen |O]]

| style="background-color:#FFFD9F;" | [[fluorine |F]]

| style="background-color:#9BCDFD;" | [[neon |Ne]]

| style="background-color:#FC9A9B;" | [[silicon |Si]]

| style="background-color:#FFFFFF;" | [[phosphorus |P]]

| style="background-color:#FFFFFF;" | [[sulfur |S]]

| style="background-color:#FFFD9F;" | [[chlorine |Cl]]

| style="background-color:#9BCDFD;" | [[argon |Ar]]

| style="background-color:#FC9A9B;" | [[germanium |Ge]]

| style="background-color:#FC9A9B;" | [[arsenic |As]]

| style="background-color:#FFFFFF;" | [[selenium |Se]]

| style="background-color:#FFFD9F;" | [[bromine |Br]]

| style="background-color:#9BCDFD;" | [[krypton |Kr]]

| style="background-color:#FC9A9B;" | [[antimony |Sb]]

| style="background-color:#FC9A9B;" | [[tellurium |Te]]

| style="background-color:#FFFD9F;" | [[iodine |I]]

| style="background-color:#9BCDFD;" | [[xenon |Xe]]

| style="background-color:#9BCDFD;" | [[radon |Rn]]

Five nonmetals—hydrogen, carbon, nitrogen, oxygen, and silicon—form the bulk of the directly observable structure of the Earth: about 73% of the [[Earth's crust|crust]], 93% of the [[biomass (ecology)|biomass]], 96% of the [[hydrosphere]], and over 99% of the [[Earth's atmosphere|atmosphere]], as shown in the accompanying table. Silicon and oxygen form highly stable tetrahedral structures, known as [[silicate mineral|silicates]]. Here, "the powerful bond that unites the oxygen and silicon ions is the cement that holds the Earth's crust together."<ref>[[#Klein|Klein & Dutrow 2007, p. 435]]{{Broken anchor|date=2024-07-17|bot=User:Cewbot/log/20201008/configuration|target_link=#Klein|reason= }}</ref>

Many have domestic and industrial applications in household accoutrements;<ref>[[#Emsley2011|Emsley 2011, pp.&nbsp;39, 44, 80–81, 85, 199, 248, 263, 367, 478, 531, 610]]; [[#Smulders|Smulders 2011, pp.&nbsp;416–421]]; [[#Chen|Chen 1990, part 17.2.1]]; [[#Hall|Hall 2021, p.&nbsp;143]]: H (primary constituent of water); He (party balloons); B (in [[detergent]]s); C (in [[pencil]]s, as graphite); N ([[Widget (beer)|beer widgets]]); O (as [[peroxide]], in [[detergents]]); F (as [[fluoride]], in [[toothpaste]]); Ne (lighting); Si (in glassware); P ([[matches]]); S (garden treatments); Cl ([[bleach]] constituent); Ar ([[insulated windows]]); Ge (in [[wide-angle lens|wide-angle camera lenses]]); Se ([[glass]]; [[solar cells]]); Br (as [[bromide]], for purification of spa water); Kr (energy saving [[fluorescent lamps]]); Sb (in batteries); Te (in [[ceramic]]s, solar panels, [[DVD recordable|rewrite-able DVD]]s); I (in [[antiseptic]] solutions); Xe (in [[plasma TV]] display cells, a technology subsequently made redundant by low cost [[LED]] and [[OLED display]]s.</ref>{{efn|Radon sometimes occurs as potentially hazardous indoor pollutant<ref>[[#Maroni|Maroni 1995, pp.&nbsp;108–123]]</ref>}} medicine and pharmaceuticals;<ref name="Imberti">[[#Imberti|Imbertierti 2020]]: H, He, B, C, N, O, F, Si, P, S, Cl, Ar, As, Se, Br, Kr, Sb, Te, I, Xe and Rn</ref> and [[laser]]s and lighting.<ref name="L&L">[[#Csele|Csele 2016]]; [[#Winstel|Winstel 2000]]; [[#Davis|Davis et al. 2006, p.&nbsp;431–432]]; [[#Grondzik|Grondzik et al. 2010, p.&nbsp;561]]: Cl, Ar, Ge, As, Se, Br, Kr, Te, I and Xe</ref> They are components of [[mineral acid]]s;<ref>[[OED|Oxford English Dictionary]]; [[#Eagleson1994|Eagleson 1994]] (all bar [[germanic acid]]); [[#Wiberg|Wiberg 2001, p.&nbsp;897]], germanic acid: H, B, C, N, O, F, Si, P, S, Cl, Ge, As, Sb, Br, Te, I and Xe</ref> and prevalent in [[plug-in hybrid]] vehicles;<ref>[[#Bhuwalka|Bhuwalka et al. 2021, pp.&nbsp;10097–10107]]: H, He, B, C, N, O, F, Si, P, S, Cl, Ar, Br, Sb, Te and I</ref> and [[smartphone]]s.<ref>[[#KingAH|King 2019, p.&nbsp;408]]: H, He, B, C, N, O, F, Si, P, S, Cl, Ge, As, Se, Br, Sb</ref>

File:Circuit Breaker 115 kV.jpg|A high-voltage [[Sulfur hexafluoride circuit breaker|circuit-breaker]] employing [[sulfur hexafluoride]] (SF₆) as its inert (air replacement) interrupting medium<ref>[[#Bolin|Bolin 2017, p.&nbsp;2-1]]{{Broken anchor|date=2024-05-31|bot=User:Cewbot/log/20201008/configuration|target_link=#Bolin|reason= The anchor (Bolin) [[Special:Diff/1226404653|has been deleted]].}}</ref>|alt=a small electricity-conducting installation in a snow-covered landscape

== Taxonomical history ==

| {{mono|1911}} || [[Cation]] formation<ref>[[#Beach|Beach 1911]]</ref>{{dubious|date=August 2024}} || C

| {{mono|1927}} || [[Goldhammer-Herzfeld criterion for metallization|Goldhammer-Herzfeld]]<br/>[[Goldhammer-Herzfeld criterion for metallization|metallization criterion]]{{efn|The Goldhammer-Herzfeld ratio is roughly equal to the cube of the atomic radius divided by the [[molar volume]].<ref>[[#Edwards1983|Edwards & Sienko 1983, p. 693]]</ref> More specifically, it is the ratio of the force holding an individual atom's [[valence electron|outer electron]]s in place with the forces on the same electrons from interactions ''between'' the atoms in the solid or liquid element. When the interatomic forces are greater than, or equal to, the atomic force, outer electron itinerancy is indicated and metallic behavior is predicted. Otherwise nonmetallic behavior is anticipated.}}<ref>[[#Herzfeld|Herzfeld 1927]]; [[#Edwards2000|Edwards 2000, pp. 100–103]]</ref> || P

| {{mono|1956}} || [[temperature coefficient of resistivity|Temperature coefficient]]<br/>[[temperature coefficient of resistivity|of resistivity]]<ref>{{Cite journal |lastlast1=Butera |firstfirst1=Richard A. |last2=Waldeck |first2=David H. |date=September 1997 |title=The Dependence of Resistance on Temperature for Metals, Semiconductors, and Superconductors |url=https://pubs.acs.org/doi/abs/10.1021/ed074p1090 |journal=Journal of Chemical Education |language=en |volume=74 |issue=9 |pages=1090 |doi=10.1021/ed074p1090 |bibcode=1997JChEd..74.1090B |issn=0021-9584}}</ref> || C

| {{mono|1999}} || Element structure (in bulk)<ref name="Scott">[[#Scott|Scott 2001, p. 1781]]</ref>{{dubious|date=August 2024}} || P

| {{mono|2020}} || [[Mott insulator#Mott criterion|Mott parameter]]{{efn|The Mott parameter is ''N''&thinsp;^1/3''ɑ*_{<small>H</small>}'' where ''N'' the number of atoms per unit volume, and ''ɑ*_{<small>H</small>}'' "is their effective size, usually taken as the effective Bohr radius of the maximum in the outermost (valence) electron probability distribution." In ambient conditions, a value of 0.45 is given for the value for the dividing line between metals and nonmetals.}}<ref>{{cite journal |vauthors=Yao B, Kuznetsov VL, Xiao T, etal|date=2020 |title= Metals and non-metals in the periodic table|journal= Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences|volume=378 |issue=2180 |pages=1–21 |doi=10.1098/rsta.2020.0213  |pmid=32811363 |pmc=7435143|bibcode=2020RSPTA.37800213Y }}</ref><ref>[[#Benzhen|Benzhen et al. 2020, p. 13]]</ref> || A

FromMuch of the mid-1700searly analyses were phenomenological, and a variety of physical, chemical, and atomic properties have been suggested for distinguishing metals from nonmetals (or other bodies),; asa listedcomprehensive inearly theset accompanyingof table.characteristics Somewas ofstated theby earliest[[Thaddeus recordedMason propertiesHarris|Rev areThaddeus theMason (high)Harris]]<nowiki/>n densityin andthe (good)1803 electrical''[[Minor conductivityEncyclopedia]]'' of.<ref metalsname="Harris 1803, p. 274"/>

Hare and BacheJohnson<ref name="HareJ66">[[#Johnson1966|Johnson 1966, pp. 3–6, 15]]</ref> observedhas thata thesimilar lineapproach ofto demarcationMason, distinguishing between metals and nonmetals hadon beenthe "annihilated"basis byof thetheir discoveryphysical ofstates, alkalineelectrical metalsconductivity, havingmechanical aproperties, densityand lessthe thanacid-base thatnature of watertheir oxides:

There is not full agreement about the use of phenomenological properties. [[John Emsley|Emsley]]<ref>[[#Emsley1971|Emsley 1971, p. 1]]</ref> pointed out the complexity of this task, asserting that no single property alone can unequivocally assign elements to either the metal or nonmetal category. Some authors divide elements into metals, metalloids, and nonmetals, but Oderberg<ref>[[#Oderberg|Oderberg 2007, p. 97]]</ref> disagrees, arguing that by the principles of categorization, anything not classified as a metal should be considered a nonmetal.

| phosphorus, sulfur, selenium, brittle{{efn|All four have less stable non-brittle forms: carbon as [[Graphite#Expanded graphite|exfoliated (expanded) graphite]],<ref name="Chung">[[#Chung|Chung 1987]]</ref><ref> [[#Godfrin|Godfrin & Lauter 1995, pp. 216‒218]]</ref> and as [[carbon nanotube]] wire;<ref name="Janas">[[#Janas|Janas, Cabrero-Vilatela & Bulmer 2013]]</ref> phosphorus as white phosphorus (soft as wax, pliable and can be cut with a knife, at room temperature);<ref name="Holderness 1979, p. 255" /> sulfur as plastic sulfur;<ref name="ReferenceE" /> and selenium as selenium wires.<ref name="ReferenceF" />}}

* <span id="Carrasco">Carrasco et al. 2023, "Antimonene: a tuneable post-graphene material for advanced applications in optoelectronics, catalysis, energy and biomedicine", ''[[Chemical Society Reviews]]'', vol. 52, no. 4, p. &nbsp;1288–1330, {{doi|10.1039/d2cs00570k}}</span>

* <span id="Chapin">Chapin FS, Matson PA & Vitousek PM 2011, Earth’sEarth's climate system, in ''Principles of Terrestrial Ecosystem Ecology,'' Springer, New York,  {{isbn|978-1-4419-9503-2}}</span>

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* <span id="Cressey">Cressey D 2010, [http://blogs.nature.com/news/2010/11/chemists_redefine_hydrogen_bon.html "Chemists re-define hydrogen bond"] {{Webarchive|url=https://web.archive.org/web/20190124163616/http://blogs.nature.com/news/2010/11/chemists_redefine_hydrogen_bon.html |date=2019-01-24 }}, ''[[Nature (journal)|Nature]] newsblog'', accessed August 23, 2017</span>

* <span id="Dorsey">Dorsey MG 2023, ''Holding Their Breath: How the Allies Confronted the Threat of Chemical Warfare in World War II'', Cornell University Press, Ithaca, New York, pp. 12-13&nbsp;12–13, {{isbn|978-1-5017-6837-8}}</span>

* <span id="Douglade">Douglade J, Mercier R 1982, Structure cristalline et covalence des liaisons dans le sulfate d’arsenic(III), As₂(SO₄)₃, ''[[Acta_CrystallographicaActa Crystallographica#Acta_Crystallographica_Section_BActa Crystallographica Section B|Acta Crystallographica Section B Structural Crystallography and Crystal Chemistry]]'', vol. 38, no, 3, 720–723, {{doi|10.1107/s056774088200394x}}</span>

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