Editing Nonmetal (section)

===Physical===
{{hatnote|See also {{slink||Physical properties by element type}}}}

{{multiple image|perrow=3|total_width=330|caption_align=center
| align = right
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|image1=Boron R105.jpg
 |alt1=Several dozen small angular stone like shapes, grey with scattered silver flecks and highlights.
 |caption1= Boron in its β-[[rhombohedral]] phase
|image2=Graphite2.jpg
 |alt2=A shiny grey-black cuboid nugget with a rough surface.
 |caption2= Metallic appearance of [[carbon]] as [[graphite]]
|image3=Liquid oxygen in a beaker 4.jpg
 |alt3=A pale blue liquid in a clear beaker
 |caption3= Blue color of [[liquid oxygen]]
|image4=Liquid fluorine tighter crop.jpg
 |alt4=A glass tube, is inside a larger glass tube, has some clear yellow liquid in it
 |caption4= Pale yellow liquid fluorine in a [[cryogenics|cryogenic bath]]
|image5=Sulfur-sample.jpg
 |alt5=Yellow powdery chunks
 |caption5= [[Sulfur]] as yellow chunks
|image6=Bromine_in_a_vial.png
 |alt6=A small capped jar a quarter filled with a very dark liquid
 |caption6= Liquid [[bromine]] at room temperature
|image7=Iodinecrystals.JPG
 |caption7= Metallic appearance of [[iodine]] under white light
 |alt7=Shiny violet-black colored crystalline shards.
|image8=An acrylic cube specially prepared for element collectors containing an ampoule filled with liquefied xenon.JPG
 |alt8=A partly filled ampoule containing a colorless liquid
 |caption8= Liquefied xenon
| header = {{font|size=100%|font=Sans-serif|text=Variety in color and form<br>of some nonmetallic elements}}
}}

Nonmetals vary greatly in appearance, being colorless, colored or shiny.<!-- It would be nice to say "due to the structure of their electrons" or something like that, as is mentioned w/r/t shiny solids and colorless gases, but nothing is stated about the electronics of the colored ones -->
For the colorless nonmetals (hydrogen, nitrogen, oxygen, and the noble gases), no absorption of light happens in the visible part of the spectrum, and all visible light is transmitted.<ref>[[#Wibaut|Wibaut 1951, p. 33]]: "Many substances&nbsp;...are colourless and therefore show no selective absorption in the visible part of the spectrum."</ref>
The colored nonmetals (sulfur, fluorine, chlorine, bromine) absorb some colors (wavelengths) and transmit the complementary or opposite colors. For example, chlorine's "familiar yellow-green colour&nbsp;... is due to a broad region of absorption in the violet and blue regions of the spectrum".<ref>[[#Elliot|Elliot 1929, p. 629]]</ref>{{efn|The absorbed light may be converted to heat or re-emitted in all directions so that the emission spectrum is thousands of times weaker than the incident light radiation.<ref>[[#Fox|Fox 2010, p. 31]]</ref>}} The shininess of boron, graphite (carbon), silicon, black phosphorus, germanium, arsenic, selenium, antimony, tellurium, and iodine{{efn|Solid iodine has a silvery metallic appearance under white light at room temperature. At ordinary and higher temperatures it [[sublimation (phase transition)|sublimes]] from the solid phase directly into a violet-colored vapor.<ref>[[#Tidy|Tidy 1887, pp. 107–108]]; [[#Koenig|Koenig 1962, p. 108]]</ref>}} is a result of the electrons reflecting incoming visible light.<ref>[[#Wiberg|Wiberg 2001, p. 416]]; Wiberg is here referring to iodine.</ref>

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 (being either hard and brittle, or soft and crumbly),<ref name="ReferenceA">[[#Johnson1966|Johnson 1966, p. 4]]</ref> and a wide range of electrical conductivity.{{efn|The solid nonmetals have electrical conductivity values ranging from 10<sup>−18</sup> S•cm<sup>−1</sup> for sulfur<ref name="A&W"/> to 3 × 10<sup>4</sup> in graphite<ref name="Jenkins">[[#Jenkins|Jenkins & Kawamura 1976, p. 88]]</ref> or 3.9 × 10<sup>4</sup> for [[arsenic]];<ref>[[#Carapella|Carapella 1968, p. 30]]</ref> cf. 0.69 × 10<sup>4</sup> for [[manganese]] to 63 × 10<sup>4</sup> for [[silver]], both metals.<ref name="A&W">[[#Aylward|Aylward & Findlay 2008, pp. 6–12]]</ref> The conductivity of graphite and arsenic (both semimetals) exceed that of manganese.}}

This diversity stems from variability in crystallographic 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 selenium atoms,<ref>{{Cite journal |last1=Corb |first1=B.W. |last2=Wei |first2=W.D. |last3=Averbach |first3=B.L. |date=1982 |title=Atomic models of amorphous selenium |url=https://linkinghub.elsevier.com/retrieve/pii/0022309382900163 |journal=Journal of Non-Crystalline Solids |language=en |volume=53 |issue=1–2 |pages=29–42 |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. Nonmetals closer to the left or bottom of the periodic table (and so closer to the metals) often have [[Metallic bonding|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>

{|class="wikitable floatright" style="line-height: 1.3; font-size: 95%; margin-left:20px; margin-bottom:1.2em"
|+ Some general physical differences<br />between elemental metals and nonmetals<ref name="Kneen"/>
|-
! Aspect !! Metals !! Nonmetals
|-
|Appearance<br>and form
|Shiny if freshly prepared<br>or fractured; few colored;<ref>[[#Taylor|Taylor 1960, p. 207]]; [[#Brannt|Brannt 1919, p. 34]]</ref><br>all but one solid<ref name="Green">[[#Green|Green 2012, p. 14]]</ref>
|Shiny, colored or<br>transparent;<ref>[[#Spencer|Spencer, Bodner & Rickard 2012, p. 178]]</ref> all but<br>one solid or gaseous<ref name="Green"/>
|-
|[[Density]]
| Often higher
| Often lower
|-
| [[Plasticity (physics)|Plasticity]]
| Mostly malleable<br />and ductile
| Often brittle solids
|-
| [[Electrical conductivity|Electrical]]<br>[[Electrical conductivity|conductivity]]<ref>[[#Redmer|Redmer, Hensel & Holst 2010, preface]]</ref>
| Good
| Poor to good
|-
| [[Electronic band structure|Electronic]]<br>[[Electronic band structure|structure]]<ref name="K&W"/>
| Metal or [[semimetal]]ic
| Semimetal,<br>[[semiconductor]],<br>or [[insulator (electricity)|insulator]]
|}
Covalently bonded nonmetals often share only the electrons required to achieve a noble gas electron configuration.<ref>[[#DeKock|DeKock & Gray 1989, pp. 423, 426—427]]</ref> For example, nitrogen forms diatomic molecules featuring a triple bonds between each atom, both of which thereby attain the configuration of the noble gas neon. In contrast antimony has buckled layers in which each antimony atom is singly bonded with three other nearby atoms.<ref>[[#Boreskov|Boreskov 2003, p. 45]]</ref>

Good electrical conductivity occurs when there is [[metallic bond]]ing,<ref name="Ashcroft and Mermin">[[Ashcroft and Mermin]]</ref> however the electrons in some nonmetals are not metallic.<ref name="Ashcroft and Mermin"/> 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<sup>−1</sup> K<sup>−1</sup> 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<sup>−1</sup> × 10<sup>4</sup> for [[manganese]] to 63 × 10<sup>4</sup> for [[silver]]; cf. carbon 3 × 10<sup>4</sup>,<ref name="Jenkins"/> arsenic 3.9 × 10<sup>4</sup> and antimony 2.3 × 10<sup>4</sup>.<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 ([[phonons]] 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,<ref name="ReferenceA"/> where [[dislocations]] cannot readily move so they tend to undergo [[brittle fracture]] rather than deforming.<ref>{{Cite book |last1=Weertman |first1=Johannes |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> [[allotropes of sulfur#Amorphous sulfur|plastic sulfur]],<ref name="ReferenceE">[[#Partington1944|Partington 1944, p. 405]]</ref> and 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 name=":1">{{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>

====Allotropes====
{{multiple image
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| image1            = Diamond-dimd15a.jpg
| alt1              = A clear triangular crystal with a flat face and slightly rough edges
| caption1          = A transparent electrical{{nbsp}}insulator
| image2            = C60-Fulleren-kristallin (cropped).JPG
| alt2              = a haphazard aggregate of brownish crystals
| caption2          = A brownish semiconductor
| image3            = Graphite-233436.jpg
| alt3              = A black multi-layered lozenge-shaped rock
| caption3          = A blackish semimetal
| header            = Three allotropes of carbon
| footer            = From left to right, [[diamond]], [[buckminsterfullerene]], and [[graphite]]
| caption_align     = center
| footer_align      = center
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{{Main list|Allotropy#Non-metals|Single-layer materials}}
Over half of the nonmetallic elements exhibit a range of less stable allotropic forms, each with distinct physical properties.<ref>[[#Barton|Barton 2021, p. 200]]</ref> For example, carbon, the most stable form of which is [[graphite]], can manifest as [[diamond]], [[buckminsterfullerene]],<ref>[[#Wiberg|Wiberg 2001, p. 796]]</ref> [[amorphous]]<ref>[[#Shang|Shang et al. 2021]]</ref> and [[Paracrystallinity|paracrystalline]]<ref>[[#Tang|Tang et al. 2021]]</ref> variations. Allotropes also occur for nitrogen, oxygen, phosphorus, sulfur, selenium and iodine.<ref>[[#Steudel|Steudel 2020, ''passim'']]; [[#Carrasco|Carrasco et al. 2023]]; [[#Shanabrook|Shanabrook, Lannin & Hisatsune 1981, pp. 130–133]]</ref>