THC Science

**Periodic table extract showing nonmetallic elements** (including the metalloids). H is normally placed over Li in Group 1. It is shown here over F for comparative purposes. The asterisks show further alternative positions for H.^[1] Nearby metals are shown with light-gray lettering, as are elements whose bulk chemistry is not well attested.

In chemistry, a nonmetal (or non-metal) is a chemical element that is a gas, liquid or brittle solid in its most stable form and which usually gains or shares electrons in chemical reactions. Typical nonmetals have a dull appearance, relatively low melting points, boiling points, and densities, and are poor conductors of heat and electricity. Chemically, nonmetals tend to have higher values of ionization energy, electron affinity, and electronegativity, and their oxides are acidic. Most or some nonmetals share a range of other properties; a few have properties that are anomalous.

Of the twenty-three elements generally counted as having nonmetallic properties many are gases: hydrogen, helium, nitrogen, oxygen, fluorine, neon, chlorine, argon, krypton, xenon and radon; one is a liquid: bromine; and as many are solids: carbon, phosphorus, sulfur and selenium, iodine, and the six elements commonly recognized as metalloids (which behave chemically predominately as nonmetals).

Three or four subclasses of nonmetals can be discerned: nonmetal halogens; noble gases; unclassified nonmetals; and (possibly) metalloids. The latter may or may not be recognized as a class separate from both metals and nonmetals. For comparative purposes they are treated here as nonmetallic elements—or a kind of nonmetal—given their predominately weak nonmetallic chemistry. The unclassified nonmetals, on a net basis, are moderately nonmetallic. The nonmetal halogens are more electronegative, and characterized by stronger nonmetallic properties and a tendency to form predominantly ionic compounds with metals. The noble gases are distinguished by their reluctance to form compounds.

The distinction between nonmetal subclasses is not absolute. Boundary overlaps, including with the metalloids, occur as outlying elements among each nonmetal subclass show or begin to show less-distinct, hybrid-like, or atypical properties.

Although five times more elements are metals than nonmetals, two of the nonmetals—hydrogen and helium—make up over 99 percent of the observable universe.^[2] Another nonmetal, oxygen, makes up almost half of the Earth's crust, oceans, and atmosphere.^[3] Living organisms are composed almost entirely of the nonmetals hydrogen, oxygen, carbon, and nitrogen.^[4] Nonmetals form many more compounds than do metals.^[5]

Definition and applicable elements

There is no rigorous definition of a nonmetal. Broadly, any element lacking a preponderance of metallic properties can be regarded as a nonmetal. Since metalloids lack such a preponderance, and are more closely allied to the non-metals in their chemical behaviour,^[6] they are here counted as such including for comparative purposes.^{[n 1]} Some variation may be encountered among authors as to which elements are regarded as nonmetals.

The twenty-three elements counted as nonmetals in this article number one in group 1 (hydrogen); one in group 13 (boron); three in group 14 (carbon, silicon, and germanium); four in group 15 (nitrogen, phosphorus, arsenic, and antimony); four in group 16 (oxygen, sulfur, selenium, and tellurium); most of group 17 (fluorine, chlorine, bromine and iodine); and all the natural elements of group 18.

Boron, shown here in the form of its β-rhombohedral phase (its most thermodynamically stable form)^[8]
Carbon (as graphite). Delocalized valence electrons within the layers of graphite give it a metallic appearance.^[9]
Liquid oxygen boiling. The higher density of LOX increases the likelihood of excitation interactions between two O₂ molecules and a photon that result in a blue colour.^[10]
Sulfur has the form of a yellow-looking powder or crystal(s). When melted and cooled quickly it forms rubbery ribbons of plastic sulfur, an allotropic form.
Black, glassy amorphous selenium (coated with a thin layer of grey selenium) and red amorphous selenium. It has a brittle comportment and low electrical conductivity.^[11]
Iodine crystals under white light have a metallic lustre.^[12]

Origin and use of the term

The distinction between metals and nonmetals arose, in a convoluted manner, from a crude recognition of natural kinds^{[n 2]} of matter. Thus, matter could be divided into pure substances and mixtures; pure substances eventually could be distinguished as compounds and elements; and "metallic" elements seemed to have broadly distinguishable attributes that other elements did not , such as their capacity to conduct heat or for their "earths" (oxides) to form basic solutions in water, quicklime CaO for example^[16] (see the taxonomy table in this section). Use of the word "nonmetal" can be traced to as far back as Lavoisier's 1789 work Traité élémentaire de chimie in which he distinguished between simple metallic and nonmetallic substances.^{[n 3]}

Properties

Atomic radii (Å) of the nonmetallic
elements in periods 1 to 6, by subclass^{[n 4]}
Period	Metalloid	Unclassified nonmetal	Nonmetal halogen	Noble gas
1	–	2.05	–	1.34
2	2.05	1.9 to 1.71	1.63	1.56
3	2.32	2.23 to 2.14	2.06	1.97
4	2.34 to 2.31	2.24	2.19	2.12
5	2.46 to 2.42	–	2.38	2.32
6	–	–	–	2.43
Average	2.23	1.94	2.10	1.96
On a period by period basis, atomic radii decrease from left right, corresponding to an increase in nonmetallic character. The unclassified nonmetals have the smallest average atomic radius of the four subclasses since: (i) they number four period 1 and 2 nonmetals, whereas the metalloids and nonmetal halogens include just one period 2 nonmetal, and while the noble gases have one period 1 nonmetal, they have one in period 5 and one in period 6; and (ii) they have anomalously small radii for the reasons set out in the complications subsection.

Property spans and average values
for the subclasses of nonmetallic elements
Property	Metalloid	Unclassified nonmetal	Nonmetal halogen	Noble gas
Ionization energy (kJ mol⁻¹)
Span	768 to 953	947 to 1,320	1,015 to 1,687	1,037 to 2,372
Average	855	1,158	1,276	1,590
Electron affinity (kJ mol⁻¹)
Span	27 to 190	−0.07 to 200	295 to 349	−120 to −50
Average	108	134	324	−79
Electronegativity (Allred-Rochow)
Span	1.9 to 2.18	2.19 to 3.44	2.66 to 3.98	2.1 to 5.2
Average	2.05	2.65	3.19	3.38
Standard reduction potential (V)
Span	−0.91 to 0.93	0.00 to 2.08	0.53 to 2.87	2.12 to 2.26
Average	−0.09	0.55	1.48	2.26
Average values of ionization energy, electron affinity, electronegativity,^{[n 5]} and standard reduction potential generally show a left to right increase consistent with increased nonmetallic character. Electron affinity values collapse at the noble gases due to their filled outer orbitals. Electron affinity can be defined as, "the energy required to remove the electron of a gaseous anion of −1 charge to produce a gaseous atom of that element e.g. Cl⁻(g) → e⁻ = 348.8 kJ mol⁻¹"; the zeroth ionization energy, in other words.^[18] The standard reduction potentials are for stable species in water, at pH 0, within the range -3 to 3 V.^[19]^{[n 6]} The values in the noble gas column are for xenon only.

Cross-class properties are the main focus of this section; the subclasses mentioned in the tables are elaborated in the section after this one. See also: Properties of nonmetals (and metalloids) by group.

Physically, nearly all nonmetals exist as either diatomic or monatomic gases, or polyatomic solids having more substantial (open-packed) forms, and have relatively small atomic radii. Metals, in contrast, are nearly all solid and close-packed, and mostly have larger atomic radii.^[20] If solid, nonmetals have a submetallic appearance (with the exception of sulfur) and are brittle, as opposed to metals, which are lustrous, and generally ductile or malleable; they usually have lower densities than metals; are mostly poorer conductors of heat and electricity; and tend to have significantly lower melting points and boiling points than those of most metals.^[21]

Chemically, the nonmetals mostly have higher ionization energies, higher electron affinities (nitrogen and the noble gases have negative electron affinities), higher electronegativity values, and higher standard reduction potentials than metals noting that, in general, the higher an element's ionization energy, electron affinity, electronegativity, or standard reduction potentials, the more nonmetallic that element is.^[22] Nonmetals, including (to a limited extent) xenon and probably radon, usually exist as anions or oxyanions in aqueous solution;^[23] they generally form ionic or covalent compounds when combined with metals (unlike metals, which mostly form alloys with other metals); and have acidic oxides whereas the common oxides of nearly all metals are basic.^[24]

Complications

Complicating the chemistry of the nonmetals is the first row anomaly seen particularly in hydrogen, (boron), carbon, nitrogen, oxygen and fluorine; and the alternation effect seen in (arsenic), selenium and bromine.^[25] The first row anomaly largely arises from the electron configurations of the elements concerned.

Hydrogen is noted for the different ways it forms bonds. It most commonly forms covalent bonds.^[26] It can lose its single valence electron in aqueous solution, leaving behind a bare proton with tremendous polarising power. This subsequently attaches itself to the lone electron pair of an oxygen atom in a water molecule, thereby forming the basis of acid-base chemistry.^[27] A hydrogen atom in a molecule can form a second, weaker, bond with an atom or group of atoms in another molecule. Such bonding, "helps give snowflakes their hexagonal symmetry, binds DNA into a double helix; shapes the three-dimensional forms of proteins; and even raises water's boiling point high enough to make a decent cup of tea."^[28]

From (boron) to neon, since the 2p subshell has no inner analogue and experiences no electron repulsion effects it consequently has a relatively small radius, unlike the 3p, 4p and 5p subshells of heavier elements^[29] (a similar effect is seen in the 1s elements, hydrogen and helium). Ionization energies and electronegativities among these elements are consequently higher than would otherwise be expected, having regard to periodic trends. The small atomic radii of carbon, nitrogen, and oxygen facilitates the formation of triple or double bonds.^[30]

Period four elements immediately after the first row of the transition metals, such as selenium and bromine, have unusually small atomic radii because the 3d electrons are not effective at shielding the increased nuclear charge, and smaller atomic size correlates with higher electronegativity.^[31]

The larger atomic radii of the heavier group 15–18 nonmetals, which enable higher bulk coordination numbers, and result in lower electronegativity values which better tolerate higher positive charges, means they are able to exhibit valences other than the lowest for their group (that is, 3, 2, 1, or 0) for example in PCl₅, SF₆, IF₇, and XeF₂.^[32]

Subclasses

Immediately to the left of most nonmetals on the periodic table are metalloids such as boron, silicon, and germanium, which generally behave chemically like (weak) nonmetals.^[33] In this sense they can be regarded as the least nonmetallic or most metallic of the nonmetallic elements.

To the left of the noble gases are the nonmetal halogens (fluorine, chlorine, bromine, and iodine) with their reactive and strongly electronegative character representing the epitome of nonmetallic character.^[34]^{[n 7]}

The remaining (unclassified) nonmetals are hydrogen, carbon, nitrogen, oxygen, phosphorus, sulfur and selenium.

As with classification schemes generally, there is some variation and overlapping of properties within and across each subclass. One or more of the metalloids are sometimes formally classified as nonmetals.^[36] Carbon, phosphorus, selenium, iodine border the metalloids and show some metallic character, as does hydrogen. Among the noble gases, radon is the most metallic and begins to show some cationic behaviour, which is unusual for a nonmetal.^[37]

Metalloids

While classification practices for the metalloids vary they are included here to facilitate comparison with the nonmetals. In the literature, metalloid elements can be considered to be separate from both the metals and the nonmetals; grouped with the metals (due to some similarities of arsenic and antimony with heavy metals);^[38] regarded as nonmetals rather than metalloids;^[39] or treated as a sub-class of nonmetals.^[40]

The six elements more commonly recognized as metalloids are boron, silicon, germanium, arsenic, antimony, and tellurium. On a standard periodic table, they occupy a diagonal area in the p-block extending from boron at the upper left to tellurium at lower right, along the dividing line between metals and nonmetals shown on some periodic tables.^[41] They are called metalloids mainly in light of their metallic appearance.^[42]

While they each have a metallic appearance, they are brittle and only fair conductors of electricity. Boron, silicon, germanium, tellurium are semiconductors. Arsenic and antimony have the electronic band structures of semimetals although both have less stable semiconducting allotropes.^[43]

Chemically the metalloids generally behave like (weak) nonmetals. They have moderate ionization energies, electron affinities, electronegativity values, are moderately strong oxidising agents, and demonstrate a tendency to form alloys with metals.^[44]

Unclassified nonmetals

After the nonmetallic elements are classified as either metalloids, halogens or noble gases, the remaining seven nonmetals are hydrogen, carbon, nitrogen, oxygen, phosphorus, sulfur and selenium. They are generally regarded as being too diverse to merit a collective examination,^[45] and have also been referred to as other nonmetals.^[46] Consequently, their chemistry is taught disparately, according to their four respective groups.^[47]

In 2021 it was reported that the unclassified nonmetals could be collectively distinguished by (i) their physical and chemical character being "moderately non-metallic" on a net basis; (ii) uniquely having either a metallic, colored, or colorless appearance; (iii) an overall tendency to form covalent compounds featuring localized and catenated bonds as chains, rings, and layers; (iv) a capacity to form interstitial and refractory compounds, in light of their relatively small atomic radii and sufficiently low ionization energy values; and (v) prominent geological, biochemical (beneficial and toxic), organocatalytic, and energetic aspects.^[48]

Nonmetal halogens

Physically, fluorine and chlorine are pale yellow and yellowish green gases; bromine is a reddish-brown liquid; and iodine is a silvery metallic solid.^{[n 8]} Electrically, the first three are insulators while iodine is a semiconductor (along its planes).^[50]

Chemically, they have high ionization energies, electron affinities, and electronegativity values, and are mostly relatively strong oxidising agents. Manifestations of this status include their intrinsically corrosive nature. All four exhibit a tendency to form predominately ionic compounds with metals whereas the remaining nonmetals tend to form predominately covalent compounds with metals.^[51]

Astatine and tennessine are in the same group as the nonmetal halogens (group 17), but are expected to have metallic properties.^[52]^[53]

Noble gas

Six nonmetals are classified as noble gases: helium, neon, argon, krypton, xenon, and the radioactive radon. In conventional periodic tables they occupy the rightmost column. They are called noble gases in light of their characteristically very low chemical reactivity.

They have very similar properties, all being colorless, odorless, and nonflammable. With their closed valence shells the noble gases have feeble interatomic forces of attraction resulting in very low melting and boiling points.^[54] That is why they are all gases under standard conditions, even those with atomic masses larger than many normally solid elements.^[55]

Chemically, the noble gases have relatively high ionization energies, no or negative electron affinities, and relatively high electronegativities. Compounds of the noble gases number in the hundreds although the list continues to grow,^[56] with most of these occurring via oxygen or fluorine combining with either krypton, xenon or radon.^[57]

The status of the period 7 congener of the noble gases, oganesson (Og), is not known. It was originally predicted to be a noble gas^[58] but may instead be a fairly reactive metallic-looking semiconducting solid with an anomalously low first ionization potential, and a positive electron affinity, due to relativistic effects.^[59] On the other hand, if relativistic effects peak in period 7 at element 112, copernicium, oganesson may turn out to be a noble gas after all, albeit more reactive than either xenon or radon.^[60]

Comparison

Properties of metals and those of the (sub)classes of metalloid, unclassified nonmetal, nonmetal halogen, and noble gas are summarized in the following two tables: physical properties in loose order of ease of determination; chemical properties from general to specific; and then to descriptive. The dashed line around the metalloids denotes that, depending on the author, the elements involved may or may not be recognised as a distinct class or subclass of elements. Metals are included as a reference point.

Physical

Some cross-subclass physical properties
Physical property	Metals	Metalloids	Unclassified nonmetals	Nonmetal halogens	Noble gases
Physical property	Alkali, Alkaline earth, Lanthanide, Actinide, Transition and Post-transition metals	Boron, Silicon, Germanium, Arsenic, Antimony (Sb), Tellurium	Hydrogen, Carbon, Nitrogen, Phosphorus, Oxygen, Sulfur, Selenium	Fluorine, Chlorine, Bromine, Iodine	Helium, Neon, Argon, Krypton, Xenon, Radon
Form	solid (Hg is liquid)	solid	solid: C, P, S, Se gaseous: H, N, O	solid: I liquid: Br gaseous: F, Cl	gaseous
Appearance	lustrous	semi-lustrous^[61]	semi-lustrous: C, P, Se^[62] colorless: H, N, O colored: S	colored: F, Cl, Br semi-lustrous: I^[63]	colorless
Elasticity	mostly malleable and ductile (Hg is liquid)	brittle^[64]	• C, black P, S and Se are brittle^[65] • the same four have less stable non-brittle forms^{[n 9]}	iodine is brittle^[71]	not applicable
Structure	mainly close-packed centrosymmetrical^[72]	polyatomic^[73]	polyatomic: C, P, S, Se^[74] diatomic: H, N, O	diatomic: H, N, O, F, Cl, Br, I	monatomic
Bulk coordination number^[75]	mostly 8−12, or more	6, 4, 3, or 2	3, 2, or 1	1	0
Allotropes^[76]	• common with temperature or pressure changes	all form^[77]	known for C, P, O, S, Se	iodine is known in amorphous form^[78]	none form
Electrical conductivity	high^{[n 10]}	moderate: B, Si, Ge, Te high: As, Sb^{[n 11]}	low: H, N, O, S moderate: P, Se high: C^{[n 12]}	low: F, Cl, Br moderate: I ^{[n 13]}	low^{[n 14]}
Volatility^{[n 15]}	• low • Hg is lowest in class	• low • As is lowest in class	low: C, P, S, Se high: H, N, O	high	higher
Electronic structure^[85]	metallic (Bi is a semimetal)	semimetal or semiconductor	semimetal, semiconductor, or insulator	semiconductor (I) or insulator	insulator
Outer electrons	1–8 valence	3–6	4–6 (H has 1)	7	8 (He has 2)
Crystal structure^[86]	mainly cubic or hexagonal	rhombohedral: B, As, Sb cubic: Si, Ge hexagonal: Te	cubic: P, O hexagonal: H, C, N, Se orthorhombic: S	cubic: F orthorhombic: Cl, Br, I	cubic: Ne, Ar, Kr, Xe, Rn hexagonal: He

Chemical

Some cross-subclass chemical properties
Chemical property	Metals	Metalloids	Unclassified nonmetals	Nonmetal halogens	Noble gases
Chemical property	Alkali, Alkaline earth, Lanthanide, Actinide, Transition and Post-transition metals	Boron, Silicon, Germanium, Arsenic, Antimony (Sb), Tellurium	Hydrogen, Carbon, Nitrogen, Phosphorus, Oxygen, Sulfur, Selenium	Fluorine, Chlorine, Bromine, Iodine	Helium, Neon, Argon, Krypton, Xenon, Radon
General chemical behaviour	• strong to weakly metallic • noble metals are disinclined to react	weakly nonmetallic^{[n 16]}	moderately nonmetallic^{[n 17]}	strongly nonmetallic^[89]	• inert to nonmetallic • Rn shows some cationic behaviour^[90]
Ionization energy ‡	• relatively low • higher for noble metals • ionization energy for Hg, Rg, Ds, Cn exceeds that for some nonmetals • electronegativity values of noble metals exceed that of P	moderate	moderate to high	high	high to very high
Electron affinity ‡		moderate	moderate: H, C, O, P (N is c. zero) higher: S, Se	high	zero or less
Electronegativity ‡		moderate: • Si < Ge ≈ B ≈ Sb < Te <As	moderate (P) to high: • P < Se ≈ C < S < N < O	high: • I < Br < Cl < F	moderate (Rn) to very high
Standard reduction potential ‡		moderate	moderate to high	high	high for Xe
Non-zero oxidation states^[91]	• largely positive • negative anionic states known for most alkali and alkaline earth metals; Pt, Au^[92]	negative and positive known for all	• negative states known for all, but for H this is an unstable state • positive known for all but only exceptionally for F ^[93] and O • from −5 for B to +7 for Cl, Br, I, and At		• only positive oxidation states known, and only for heavier noble gases • from +2 for Kr, Xe, and Rn to +8 for Xe
Catenation tendency^[94]	known for group 8‒11 transition metals;^[95] and Hg, Ga, In,^[96] Sn and Bi^[97]	significant: B, Si; Te less so: Ge, As, Sb	predominant: C significant: P, S, Se less so: H, N, O	known in cationic (Cl, Br, I) and anionic forms^[98]	not known
Compounds with metals	alloys or intermetallic compounds	tend to form alloys or intermetallic compounds^[99]	mainly covalent: H†, C, N, P, S, Se mainly ionic: O ^[100]	mainly ionic: F, Cl, Br, I ^[101]	simple compounds in ambient conditions not known^{[n 18]}
Oxides	• ionic, polymeric, layer, chain, and molecular structures^[103] • V; Mo, W; Al, In, Tl; Sn, Pb; Bi are glass formers^[104] • basic; some amphoteric or acidic	• polymeric in structure^[105] • B, Si, Ge, As, Sb, Te are glass formers^[106] • amphoteric or weakly acidic^[107]^[108]^{[n 19]}	• mostly molecular^[110] • C, P, S, Se are known in at least one polymeric form • P, S, Se are glass formers;^[111] CO₂ forms a glass at 40 GPa^[112] • acidic, or neutral (H₂O, CO, NO, N₂O)	• molecular^[113] • iodine is known in at least one polymeric form, I₂O₅^[114] • no glass formers known • acidic	• molecular • XeO₂ is polymeric^[115] • no glass formers known • stable xenon oxides (XeO₃, XeO₄) are acidic
Sulfates	nearly all form^{[n 20]}	may form^{[n 21]}	most form^{[n 22]}	iodine forms an oxosulfate (IO)₂SO₄^[131]	not known
† Hydrogen can also form alloy-like hydrides^[132] ‡ The labels moderate, high, higher, and very high are based on the value spans listed in the table "Property spans and average values for the subclasses of nonmetallic elements"

Allotropes

Many nonmetals have less stable allotropes, with either nonmetallic or metallic properties. Graphite, the standard state of carbon, has a lustrous appearance and is a fairly good electrical conductor. The diamond allotrope of carbon is clearly nonmetallic, however, being translucent and having a relatively poor electrical conductivity. Carbon is also known in several other allotropic forms, including semiconducting buckminsterfullerene (C₆₀). Nitrogen can form gaseous tetranitrogen (N₄), an unstable polyatomic molecule with a lifetime of about one microsecond.^[133] Oxygen is a diatomic molecule in its standard state; it also exists as ozone (O₃), an unstable nonmetallic allotrope with a half-life of around half an hour.^[134] Phosphorus, uniquely, exists in several allotropic forms that are more stable than that of its standard state as white phosphorus (P₄). The red and black allotropes are probably the best known; both are semiconductors. Phosphorus is also known as diphosphorus (P₂), an unstable diatomic allotrope.^[135] Sulfur has more allotropes than any other element;^[136] all of these, except plastic sulfur (a metastable ductile mixture of allotropes)^[137] have nonmetallic properties. Selenium has several nonmetallic allotropes, all of which are much less electrically conducting than its standard state of grey "metallic" selenium.^[138] Iodine is also known in a semiconducting amorphous form.^[139] Under sufficiently high pressures, just over half of the nonmetals, starting with phosphorus at 1.7 GPa,^[140] have been observed to form metallic allotropes.

Most metalloids, like the less electronegative nonmetals, form allotropes. Boron is known in several crystalline and amorphous forms. The discovery of a quasispherical allotropic molecule borospherene (B₄₀) was announced in July 2014. Silicon was most recently known only in its crystalline and amorphous forms. The synthesis of an orthorhombic allotrope Si₂₄, was subsequently reported in 2014.^[141] At pressure of c. 10–11 GPa, germanium transforms to a metallic phase with the same tetragonal structure as tin; when decompressed—and depending on the speed of pressure release—metallic germanium forms a series of allotropes that are metastable at ambient condition.^[142] Arsenic and antimony form several well known allotropes (yellow, grey, and black). Tellurium is known in its crystalline and amorphous forms.^[143] All of these elements are known in the form of single-layer allotropes.

Abundance, occurrence and extraction

a lump of rock, with some yellow crystals and red crystals embedded into it — Large (up to 1.8 cm) and unusual yellow boron-rich londonite (Cs,K,Rb)Al₄Be₄(B,Be)₁₂O₂₈ crystals associated with rubellite tourmaline

Abundance

Hydrogen and helium are estimated to make up approximately 99 per cent of all ordinary matter in the universe. Less than five percent of the universe is believed to be made of ordinary matter, represented by stars, planets and living beings. The balance is made of dark energy and dark matter, both of which are currently poorly understood.^[144]

Hydrogen, carbon, nitrogen, and oxygen constitute the great bulk of the Earth's atmosphere, oceans, crust, and biosphere; the remaining nonmetals have abundances of 0.5 per cent or less. In comparison, 35 per cent of the crust is made up of the metals sodium, magnesium, aluminium, potassium and iron; together with a metalloid, silicon. All other metals and metalloids have abundances within the crust, oceans or biosphere of 0.2 per cent or less.^[145]

Occurrence

Most nonmetals occur naturally namely H, C, N, O, S, Se among the unclassified nonmetals; antimony and tellurium (occasionally) among the metalloids; and all six of the noble gases. Among the unclassified nonmetals P is too reactive to do so, as is the case (ordinarily) for the nonmetal halogens F, Cl, Br, and I. A 2012 study reported the presence of 0.04% F
₂ by weight in antozonite, attributing these inclusions to radiation from the presence of tiny amounts of uranium.^[146]

Extraction

Nonmetals, and metalloids, in their elemental forms are extracted from:^[147] brine: Cl, Br, I; liquid air: N, O, Ne, Ar, Kr, Xe; minerals: B (borate minerals); C (coal; diamond; graphite); F (fluorite); Si (silica) P (phosphates); Sb (stibnite, tetrahedrite); I (in sodium iodate NaIO₃ and sodium iodide NaI); natural gas: H, He, S; and from ores, as processing byproducts: Ge (zinc ores); As (copper and lead ores); Se, Te (copper ores); and Rn (uranium-bearing ores). Astatine is produced in minute quantities by irradiating bismuth.

Cost

The cost of most non-radioactive nonmetals is unremarkable. As at July 2021, arsenic, germanium, bromine and boron can cost from three to ten times the cost of silver (about $1 US per gram). Purchasing costs can fall dramatically if bulk quantities are involved.^[148] Black phosphorus is produced only in gram quantities by boutique suppliers—a single crystal of produced via chemical vapour transport can cost up to $1,000 US per gram (c. seventeen times the cost of gold); in contrast, red phosphorus costs about 50 cents a gram or $227 a pound.^[149] As of July 2021, polonium (a metal) was listed as being available for about $84 US per microgram;^[150] Zalutsky and Pruszynski^[151] estimated a similar cost for producing astatine. Radon does not appear to be available commercially.

Applications in common

Shared uses of nonmetallic elements
Field	Elements
cryogenics and refrigerants	H, He, N, O, F and Ne
fertilizers	H, N, P, S, Cl (as a micronutrient) and Se
household accoutrements^{[n 23]}	H (primary constituent of water); He (party balloons); C (in pencils, as graphite); N (beer widgets); O (as peroxide, in detergents); F (as fluoride, in toothpaste); Ne (lighting); P (matches); S (garden treatments); Cl (bleach constituent); Ar (insulated windows); Se (glass; solar cells); Br (as bromide, for purification of spa water); Kr (energy saving fluorescent lamps); I (in antiseptic solutions); Xe (in plasma TV display cells, a technology subsequently made redundant by low cost OLED displays).
industrial acids	C, N, F, P, S and Cl
inert air replacements	N, Ne, S (in sulfur hexafluoride SF₆), Ar, Kr and Xe
lasers and lighting	He, C (in carbon dioxide lasers, CO₂); N, O (in a chemical oxygen iodine laser); F (in a hydrogen fluoride laser, HF); Ne, S (in a sulfur lamp); Ar, Kr and Xe
medicine and pharmaceuticals	He, O, F, Cl, Br, I, Xe and Rn
plug-in hybrid vehicles	H, He, B, C, N, O, F, Si, P, S, Cl, Ar, Br, Sb, Te, I

Nonmetals have no universal or near-universal applications. This is not the case with metals, most of which have structural uses; nor the metalloids, the typical uses of which extend to (for example) oxide glasses, alloying components, and semiconductors. Shared applications of different subsets of the nonmetals instead encompass their presence in, or specific uses in the fields of cryogenics and refrigerants; fertilizers; household accoutrements; industrial acids; lasers and lighting; medicine and pharmaceuticals; and plug-in hybrid vehicles.^[153]

The number of compounds formed by nonmetals is vast.^[154] The first nine places in a "top 20" table of elements most frequently encountered in 8,427,300 compounds, as listed in the Chemical Abstracts Service register for July 1987, were occupied by nonmetals. Hydrogen, carbon, oxygen and nitrogen were found in the majority (greater than 64 per cent) of compounds. Silicon, a metalloid, was in 10th place. The highest rated metal, with an occurrence frequency of 2.3 per cent, was iron, in 11th place.^[155]

Discovery

As a time stamp, most nonmetallic elements were not discovered until after the freezing of mercury in 1759 by the German-Russian physicist Braun and the Russian polymath Lomonosov. Before then, carbon, sulfur and antimony were known in antiquity; and arsenic and phosphorus were discovered by, respectively, Albertus Magnus during the Middle Ages, and Hennig Brand during the Renaissance. In the ensuring century and a half, from 1766 to 1895, the remaining nonmetallic elements, bar radon and astatine, were isolated. Helium, in 1868, was the first element not discovered on Earth; it subsequently acquired an "-ium" suffix as it was thought there was no room left in the periodic table, at that time, for a new nonmetal.^[156] Radon was discovered at the turn of the 20th century.^{[n 24]}^{[n 25]}

Notes

^ Ontologically speaking, anything not a metal is a nonmetal.^[7]
^ A natural kind can be said to be a grouping that reflects divisions in the world, as understood at the time, rather than (so much) the interests and actions of humans. "The periodic table is considered by many authors to be a perfect illustration of how things in the world are divided into natural kinds." Since kinds are revealed by science, a science can revise which kinds it holds to exist: phlogiston was regarded as a kind until after Lavoisier's chemical revolution.^[15]
^ Subſtances ſimples non-métalliques and métalliques, as Lavoisier put it
^ Atomic radius is here defined as the average distance from the nucleus where the electron density falls to 0.001 electrons per bohr⁻³.^[17]
^ Electronegativity values for the noble gases are from Allen LC & Huheey JE 1980, "The definition of electronegativity and the chemistry of the noble gases", Journal of Inorganic and Nuclear Chemistry, vol. 42, no. 10, pp. 1523–1524.
^ No agents producing complexes or insoluble compounds are present other than HOH and OH⁻.
^ When astatine, the heavier congener of iodine, was synthesized in 1940 it was thought to be a metal. It subsequently came to be regarded as a nonmetal or a metalloid; it is now predicted to be a monatomic metal.^[35]
^ Solid iodine has a silvery metallic appearance under white light, at room temperature.^[49]
^ Carbon as exfoliated (expanded) graphite,^[66] and as metre-long carbon nanotube wire;^[67] phosphorus as white phosphorus (soft as wax, pliable and can be cut with a knife, at room temperature);^[68] sulfur as plastic sulfur;^[69] and selenium as selenium wires^[70]
^ Metals have electrical conductivity values of from 6.9 × 10³ S•cm⁻¹ for manganese to 6.3 × 10⁵ for silver.^[79]
^ Metalloids have electrical conductivity values of from 1.5 × 10⁻⁶ S•cm⁻¹ for boron to 3.9 × 10⁴ for arsenic.^[80]
^ The unclassified nonmetals have electrical conductivity values of from c. ~10⁻¹⁸ S•cm⁻¹ for the elemental gases to 3 × 10⁴ in graphite.^[81]
^ The nonmetal halogens have electrical conductivity values of from c. ~10⁻¹⁸ S•cm⁻¹ for F and Cl to 1.7 × 10⁻⁸ S•cm⁻¹ for iodine.^[82]
^ The elemental gases have electrical conductivity values of c. ~10⁻¹⁸ S•cm⁻¹^[83]
^ Based on vapor pressures of the elements [84]
^ They always give compounds less acidic in character than the corresponding compounds of the typical nonmetals^[87]
^ "The elements change from…metalloids, to moderately active nonmetals, to very active nonmetals, and to a noble gas."^[88]
^ Disodium helide (Na₂He) is a compound of helium and sodium that is stable at high pressures above 113 GPa. Argon forms an alloy with nickel, at 140 GPa and close to 1,500 K however at this pressure argon is no longer a noble gas.^[102]
^ Arsenic trioxide reacts with sulfur trioxide, forming arsenic "sulfate" As₂(SO₄)₃;^[109] see also the Sulfates row.
^ Sulfates of osmium have not been characterized with any great degree of certainty.^[116]
^ Boron is reported to be capable of forming an oxysulfate (BO)₂SO₄,^[117] a bisulfate B(HSO₄)₃^[118] and a sulfate B₂(SO₄)₃.^[119] The existence of a sulfate has been disputed.^[120] In light of the existence of silicon phosphate, a silicon sulfate might also exist.^[121] Germanium forms an unstable sulfate Ge(SO₄)₂ (d 200 °C).^[122] Arsenic forms oxide sulfates As₂O(SO₄)₂ (= As₂O₃.2SO₃)^[123] and As₂(SO₄)₃ (= As₂O₃.3SO₃).^[124] Antimony forms a sulfate Sb₂(SO₄)₃ and an oxysulfate (SbO)₂SO₄.^[125] Tellurium forms an oxide sulfate Te₂O₃(SO)₄.^[126]
^ Hydrogen forms hydrogen sulfate H₂SO₄. Carbon forms (a blue) graphite hydrogen sulfate C⁺
₂₄HSO^–
₄ • 2.4H₂SO₄.^[127] Nitrogen forms nitrosyl hydrogen sulfate (NO)HSO₄ and nitronium (or nitryl) hydrogen sulfate (NO₂)HSO₄.^[128] Phosphorus is found as the phosphosulfate PO₂SO₄⁻ group in biochemistry.^[129] There are indications of a basic sulfate of selenium SeO₂.SO₃ or SeO(SO₄).^[130]
^ Rn sometimes occurs as potentially hazardous indoor pollutant^[152]
^ Immediately following the production of astatine in 1940, early investigators considered it a metal.^[157] In 1949 it was called the most noble (difficult to reduce) nonmetal as well as being a relatively noble (difficult to oxidize) metal.^[158] In 1950 astatine was described as a halogen and (therefore) a reactive nonmetal.^[159] In 2013, on the basis of relativistic modelling, astatine was predicted to be a monatomic metal, with a face-centred cubic crystalline structure.^[160]
^ Sources for this section are Emsley,^[161] Marshall^[162] and Weeks and Leicester.^[163]

References

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Monographs

Bailey GH 1918, The Tutorial Chemistry, Part 1: The non-metals, 4th ed., W Briggs (ed.), University Tutorial Press, London
Emsley J 1971, The Inorganic Chemistry of the Non-metals, Methuen Educational, London, ISBN 978-0-423-86120-4
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Jolly WL 1966, The Chemistry of the Non-metals, Prentice-Hall, Englewood Cliffs, New Jersey
Powell P & Timms PL 1974, The Chemistry of the Non-metals, Chapman & Hall, London, ISBN 978-0-470-69570-8
Sherwin E & Weston GJ 1966, Chemistry of the Non-metallic Elements, Pergamon Press, Oxford
Steudel R 1977, Chemistry of the Non-metals: With an Introduction to Atomic Structure and Chemical Bonding, English edition by FC Nachod & JJ Zuckerman, Berlin, Walter de Gruyter, ISBN 978-3-11-004882-7
—— 2020, Chemistry of the Non-metals: Syntheses - Structures - Bonding - Applications, in collaboration with D Scheschkewitz, Berlin, Walter de Gruyter, doi:10.1515/9783110578065

External links

Media related to Nonmetals at Wikimedia Commons

[8] Ontologically speaking, anything not a metal is a nonmetal.^[7]

[17] A natural kind can be said to be a grouping that reflects divisions in the world, as understood at the time, rather than (so much) the interests and actions of humans. "The periodic table is considered by many authors to be a perfect illustration of how things in the world are divided into natural kinds." Since kinds are revealed by science, a science can revise which kinds it holds to exist: phlogiston was regarded as a kind until after Lavoisier's chemical revolution.^[15]

[19] Subſtances ſimples non-métalliques and métalliques, as Lavoisier put it

[21] Atomic radius is here defined as the average distance from the nucleus where the electron density falls to 0.001 electrons per bohr⁻³.^[17]

[22] Electronegativity values for the noble gases are from Allen LC & Huheey JE 1980, "The definition of electronegativity and the chemistry of the noble gases", Journal of Inorganic and Nuclear Chemistry, vol. 42, no. 10, pp. 1523–1524.

[25] No agents producing complexes or insoluble compounds are present other than HOH and OH⁻.

[42] When astatine, the heavier congener of iodine, was synthesized in 1940 it was thought to be a metal. It subsequently came to be regarded as a nonmetal or a metalloid; it is now predicted to be a monatomic metal.^[35]

[57] Solid iodine has a silvery metallic appearance under white light, at room temperature.^[49]

[79] Carbon as exfoliated (expanded) graphite,^[66] and as metre-long carbon nanotube wire;^[67] phosphorus as white phosphorus (soft as wax, pliable and can be cut with a knife, at room temperature);^[68] sulfur as plastic sulfur;^[69] and selenium as selenium wires^[70]

[89] Metals have electrical conductivity values of from 6.9 × 10³ S•cm⁻¹ for manganese to 6.3 × 10⁵ for silver.^[79]

[91] Metalloids have electrical conductivity values of from 1.5 × 10⁻⁶ S•cm⁻¹ for boron to 3.9 × 10⁴ for arsenic.^[80]

[93] The unclassified nonmetals have electrical conductivity values of from c. ~10⁻¹⁸ S•cm⁻¹ for the elemental gases to 3 × 10⁴ in graphite.^[81]

[95] The nonmetal halogens have electrical conductivity values of from c. ~10⁻¹⁸ S•cm⁻¹ for F and Cl to 1.7 × 10⁻⁸ S•cm⁻¹ for iodine.^[82]

[97] The elemental gases have electrical conductivity values of c. ~10⁻¹⁸ S•cm⁻¹^[83]

[99] Based on vapor pressures of the elements [84]

[103] They always give compounds less acidic in character than the corresponding compounds of the typical nonmetals^[87]

[105] "The elements change from…metalloids, to moderately active nonmetals, to very active nonmetals, and to a noble gas."^[88]

[120] Disodium helide (Na₂He) is a compound of helium and sodium that is stable at high pressures above 113 GPa. Argon forms an alloy with nickel, at 140 GPa and close to 1,500 K however at this pressure argon is no longer a noble gas.^[102]

[128] Arsenic trioxide reacts with sulfur trioxide, forming arsenic "sulfate" As₂(SO₄)₃;^[109] see also the Sulfates row.

[136] Sulfates of osmium have not been characterized with any great degree of certainty.^[116]

[147] Boron is reported to be capable of forming an oxysulfate (BO)₂SO₄,^[117] a bisulfate B(HSO₄)₃^[118] and a sulfate B₂(SO₄)₃.^[119] The existence of a sulfate has been disputed.^[120] In light of the existence of silicon phosphate, a silicon sulfate might also exist.^[121] Germanium forms an unstable sulfate Ge(SO₄)₂ (d 200 °C).^[122] Arsenic forms oxide sulfates As₂O(SO₄)₂ (= As₂O₃.2SO₃)^[123] and As₂(SO₄)₃ (= As₂O₃.3SO₃).^[124] Antimony forms a sulfate Sb₂(SO₄)₃ and an oxysulfate (SbO)₂SO₄.^[125] Tellurium forms an oxide sulfate Te₂O₃(SO)₄.^[126]

[152] Hydrogen forms hydrogen sulfate H₂SO₄. Carbon forms (a blue) graphite hydrogen sulfate C⁺
₂₄HSO^–
₄ • 2.4H₂SO₄.^[127] Nitrogen forms nitrosyl hydrogen sulfate (NO)HSO₄ and nitronium (or nitryl) hydrogen sulfate (NO₂)HSO₄.^[128] Phosphorus is found as the phosphosulfate PO₂SO₄⁻ group in biochemistry.^[129] There are indications of a basic sulfate of selenium SeO₂.SO₃ or SeO(SO₄).^[130]

[175] Rn sometimes occurs as potentially hazardous indoor pollutant^[152]

[184] Immediately following the production of astatine in 1940, early investigators considered it a metal.^[157] In 1949 it was called the most noble (difficult to reduce) nonmetal as well as being a relatively noble (difficult to oxidize) metal.^[158] In 1950 astatine was described as a halogen and (therefore) a reactive nonmetal.^[159] In 2013, on the basis of relativistic modelling, astatine was predicted to be a monatomic metal, with a face-centred cubic crystalline structure.^[160]

[188] Sources for this section are Emsley,^[161] Marshall^[162] and Weeks and Leicester.^[163]

[1] Imyanitov 2016

[2] Sukys 1999, p. 60.

[3] Bettelheim et al. 2016, p. 33.

[4] Schulze-Makuch & Irwin 2008, p. 89.

[5] Steurer 2007, p. 7.

[6] Newth 1894, p. 7−8; Friend 1914, p. 9

[7] Oderberg 2007, p. 97

[9] Van Setten et al. 2007, pp. 2460–1; Oganov et al. 2009, pp. 863–4

[10] Hill & Holman 2000, p. 124

[11] Shakhashiri, Dirreen & Williams 1989

[12] Kozyrev 1959, p. 104; Chizhikov & Shchastlivyi 1968, p. 25

[13] Vernon 2013

[14] Jesperson, Brady & Hyslop 2012, p. 8

[15] Oderberg 2007, p. 97

[16] Bird & Tobin 2018; Vernon 2021, pp. 162–163

[18] Lidin 1996, pp. 64‒65

[20] Rahm, Hoffmann & Ashcroft 2016

[23] Wulfsberg 2000, pp. 321, 354

[24] Wulfsberg 2000, pp. 274–248; Schweitzer & Pesterfield 2010, pp. 228–229, 232–233

[26] Russell & Lee 2005, pp. 1‒8

[27] Kneen, Rogers & Simpson 1972, pp. 263

[28] Yoder, Suydam & Snavely 1975, p. 58

[29] Schweitzer & Pesterfield 2010, passim

[30] Kneen, Rogers & Simpson 1972, pp. 263‒264; passim

[31] Kneen, Rogers & Simpson 1972, p. 360

[32] Lee 1996, p. 240

[33] Greenwood & Earnshaw 2002, p. 43

[34] Cressey 2010

[35] Siekierski & Burgess 2002, p. 24–25

[36] Siekierski & Burgess 2002, p. 23

[37] Kneen, Rogers & Simpson 1972, p. 362

[38] Cox 2004, p. 146

[39] Bailar et al. 1989, p. 742

[40] Lanford 1959, p. 176

[41] Hermann, Hoffmann & Ashcroft 2013

[43] Cox 2004

[44] Stein 1983, p. 165

[45] Tyler 1948, p. 105; Reilly 2002, pp. 5–6

[46] Hampel & Hawley 1976, p. 174;

[47] Goodrich 1844, p. 264; The Chemical News 1897, p. 189; Hampel & Hawley 1976, p. 191; Lewis 1993, p. 835; Hérold 2006, pp. 149–50

[48] Vernon 2013

[49] Rochow 1977, pp. 1, 4

[50] Vernon 2013

[51] Vernon 2013

[52] Vernon 2020, p. 721; Cao et al. 2021

[53] Challoner 2014, p. 5; Government of Canada 2015; Gargaud et al. 2006, p. 447

[54] Metalloids: The Chemical News 1864, p. 22; Halogens: Berzelius 1832, pp. 248–276; Noble gases: Renouf 1901, pp. 268–27

[55] Cao et al. 2021

[56] Vernon 2013

[58] Vernon 2013

[59] Greenwood & Earnshaw 2002, pp. 789‒887; Cotton et al. 1999, p. 554

[60] Hermann, Hoffmann & Ashcroft 2013

[61] GSI 2015

[62] Jolly 1966, p. 20

[63] Clugston & Flemming 2000, pp. 100–1, 104–5, 302

[64] Maosheng 2020

[65] Mazej 2020

[66] Seaborg 1969, p. 626

[67] Nash 2005

[68] Scerri 2013, pp. 204–8

[69] Rochow 1966, passim

[70] Emsley 2011, pp. 397,480; Wiberg 2001, p. 780

[71] Vernon 2013

[72] Rochow 1966, passim

[73] Wiberg 2001, pp. 505, 681, 781; Glinka 1965, p. 356

[74] Chung 1987; Godfrin & Lauter 1995

[75] Cambridge Enterprise 2013

[76] Faraday 1853, p. 42; Holderness & Berry 1979, p. 255

[77] Partington 1944, p. 405

[78] Regnault 1853, p. 208

[80] Wiberg 2001, p. 416

[81] Russell & Lee 2005, pp. 1‒8

[82] Bell & Garofalo, p. 131

[83] Bell & Garofalo, p. 131

[84] Darken & Gurry 1953, pp. 50‒57

[85] Addison 1964

[86] Si: Shiell at al. 2021; Ge: Zhao et al. 2017; Te: Brodsky et al. 1972

[87] West 1953

[88] Desai, James & Ho 1984, p. 1160; Matula 1979, p. 1260

[90] Schaefer 1968, p. 76; Carapella 1968, p. 30

[92] Bogoroditskii & Pasynkov 1967, p. 77; Jenkins & Kawamura 1976, p. 88

[94] Bogoroditskii & Pasynkov 1967, p. 77; Greenwood & Earnshaw 2002, p. 804

[96] Bogoroditskii & Pasynkov 1967, p. 77

[98] Lide 2003; National Physical Laboratory 1995

[100] Keeler & Wothers 2013, p. 293

[101] Donohue 1982, passim

[102] Rochow 1966, p. 4

[104] Welcher 2001, p. 3-32

[106] Mackin 2014, p. 80

[107] Stein 1969; Pitzer 1975

[108] Wiberg 2001, passim

[109] Ellis 2006

[110] Pitts, Holl & Lectka 2018

[111] Wulfsberg 1987, pp. 202−206

[112] Braunstein & Danopoulos 2021

[113] Hill 2010, p. 210

[114] Riley et al. 2020

[115] Wiberg 20001, pp. 419‒422

[116] Vernon 2020, p. 223

[117] Woodward et al. 1999, p. 134

[118] Cotton et al. 1999, p. 554

[119] Dalton, Louisa (30 October 2019). "Argon reacts with nickel under pressure-cooker conditions". Chemical & Engineering News. Retrieved 6 November 2019.

[121] Wells 1984, p. 534

[122] Rao 2002, p. 22

[123] Puddephatt & Monaghan 1989, p. 59

[124] Sidorov 1960

[125] Rochow 1966, p. 4

[126] Atkins 2006 et al., pp. 8, 122–23

[127] Wiberg 2001, p. 750

[129] Puddephatt & Monaghan 1989, p. 59

[130] Rao 2002, p. 22

[131] McMillan 2006

[132] Puddephatt & Monaghan 1989, p. 59

[133] King 1995, p. 182

[134] Ritter 2011, p. 10

[135] Raub & Griffith 1980, p. 167

[137] Nemodruk & Karalova 1969, p. 48

[138] Sneed 1954, p. 472; Gillespie & Robinson 1959, p. 407

[139] Zuckerman & Hagen 1991, p. 303

[140] Sanderson 1967, p. 178

[141] Iler 1979, p. 190

[142] Sanderson 1960, p. 162; Greenwood & Earnshaw 2002, p. 387

[143] Mercier & Douglade 1982

[144] Douglade & Mercier 1982

[145] Wiberg 2001, p. 764

[146] Wickleder 2007, p. 350

[148] Wiberg 2001, p. 795

[149] Lidin 1996, pp. 266, 270; Brescia et al. 1975, p. 453

[150] Venkatachalam 2003

[151] Greenwood & Earnshaw 2002, p. 786

[153] Furuseth et al. 1974

[154] Steudel 1977, p. 176

[155] Cacace, de Petris & Troiani 2002

[156] Koziel 2002, p. 18

[157] Piro et al. 2006

[158] Steudel & Eckert 2003, p. 1

[159] Greenwood & Earnshaw 2002, pp. 659–660

[160] Moss 1952, p. 192; Greenwood & Earnshaw 2002, p. 751

[161] Shanabrook, Lannin & Hisatsune 1981

[162] Yousuf 1998, p. 425

[163] Shiell at al. 2021

[164] Zhao et al. 2017

[165] [[#Brodsky|Brodsky et al. 1972}}

[166] Ostriker & Steinhardt 2001

[167] Nelson 1987, p. 732

[168] Schmedt, Mangstl & Kraus 2012

[169] Emsley 2011, p. 428

[170] Chemicool Periodic Table

[171] Boise State University

[172] United Nuclear 2021

[173] Zalutsky & Pruszynski 2011, p. 181

[174] Maroni 1995

[176] Emsley 2011, passim; Bhuwalka et al. 2021

[177] King & Caldwell 1954, p. 17; Brady & Senese 2009, p. 69

[178] Nelson 1987, p. 735

[179] Smith 1975

[180] Vasáros & Berei 1985, p. 109

[181] Haissinsky & Coche 1949, p. 400

[182] Brownlee et al. 1950, p. 173

[183] Hermann, Hoffmann & Ashcroft 2013

[185] Emsley 2011

[186] Marshall 2006

[187] Weeks 1968

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