Editing Nonmetal (section)

==Types {{anchor|Classes}}==
[[List of alternative nonmetal classes|Nonmetal classification schemes]] vary widely, with some accommodating as few as two subtypes and others up to seven. For example, the periodic table in the [[Encyclopaedia Britannica]] recognizes noble gases, halogens, and other nonmetals, and splits the elements commonly recognized as metalloids between "other metals" and "other nonmetals".<ref>[[#EB2021|Encyclopaedia Britannica 2021]]</ref> On the other hand, seven of twelve color categories on the Royal Society of Chemistry periodic table include nonmetals.<ref>[[#RSC2|Royal Society of Chemistry 2021]]</ref>{{efn| Of the twelve categories in the Royal Society periodic table, five only show up with the metal filter, three only with the nonmetal filter, and four with both filters. Interestingly, the six elements marked as metalloids (boron, silicon, germanium, arsenic, antimony, and tellurium) show under both filters.  Six other elements (113–118: nihonium, flerovium, moscovium, livermorium, tennessine, and oganesson), whose status is unknown, also show up under both filters but are not included in any of the twelve color categories.}}

{| class="wikitable floatright" style="font-size:120%;text-align:center; line-height: 95%;border-color:black;"
|-style="font-size:70% ; line-height: 95%;"
| style="border:none"|
| colspan=1 style="border:none;" |
| colspan=4 style="border:none;" |  '''Group''' (1, 13−18)
| colspan=2 style="border:none;text-align:right" |  '''Period'''
|-style="font-size:70% ; line-height: 95%; vertical-align:top;"
| style="border:none"|
| scope="col" style="border:none; width: 22px" | 13
| scope="col" style="border:none; width: 22px" | 14
| scope="col" style="border:none; width: 22px" | 15
| scope="col" style="border:none; width: 22px" | 16
| scope="col" style="border:none; width: 22px" | <u>1</u>/17
| scope="col" style="border:none; width: 22px" | 18
| scope="col" style="border:none; width: 22px" | {{nowrap|(1−6)}}
|-
| style="border:none; line-height: 20px"| &nbsp;
| colspan=4 style="border:none" |
| 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="border:none; font-size:70%;" | '''1'''
|-
| style="border:none; line-height: 20px"| &nbsp;
| 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="border:none; font-size:70%" | '''2'''
|-
| style="border:none; line-height: 20px"| &nbsp;
| style="border:none;" | 
| 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="border:none; font-size:70%" | '''3'''
|-
| style="border:none; line-height: 20px"| &nbsp;
| style="border:none;" |
| 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="border:none; font-size:70%" | '''4'''
|-
| style="border:none; line-height: 20px"| &nbsp;
| colspan=2 style="border:none;" |
| 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="border:none; font-size:70%" | '''5'''
|-
| style="border:none; line-height: 20px"| &nbsp;
| colspan=5 style="border:none;" |
| style="background-color:#9BCDFD;" | [[radon|Rn]]
| style="border:none; font-size:70%" | '''6'''
|-
|-
| colspan=8 style="border:none;" |
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{{legend|#9BCDFD|Noble gas}}
{{legend|#FFFD9F|Halogen nonmetals}}
{{legend|#FFFFFF|Other nonmetals}}
{{legend|#FC9A9B|Metalloida}}
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Starting on the right side of the periodic table, three types of nonmetals can be recognized:

<div style="margin-left:2em; text-indent:-2em;">
{{legend inline|#9BCDFD|size=110%}} the inert noble gases—helium, neon, argon, krypton, xenon, radon;<ref name="Matson"/></div>

<div style="margin-left:2em; text-indent:-2em;">
{{legend inline|#FFFD9F|size=110%}} the reactive halogen nonmetals—fluorine, chlorine, bromine, iodine;<ref>[[#Kernion|Kernion & Mascetta 2019, p. 191]]; [[#Cao|Cao et al. 2021, pp. 20–21]]; [[#Hussain|Hussain et al. 2023]]; also called "nonmetal halogens": [[#Chambers1982|Chambers & Holliday 1982, pp. 273–274]]; [[#Bohlmann|Bohlmann 1992, p. 213]]; [[#Jentzsch|Jentzsch & Matile 2015, p. 247]] or "stable halogens": [[#Vassilakis|Vassilakis, Kalemos & Mavridis 2014, p. 1]]; [[#Hanley|Hanley & Koga 2018, p. 24]]; [[#Kaiho|Kaiho 2017, ch.&nbsp;2, p. 1]]</ref> and</div>

<div style="margin-left:2em; text-indent:-2em;">
{{legend inline|#FFFFFF|size=110%}} the mixed reactivity "unclassified nonmetals", a set with no widely used collective name—hydrogen, carbon, nitrogen, oxygen, phosphorus, sulfur, selenium.{{efn|Varying configurations of these nonmetals have been referred to as, for example, basic nonmetals,<ref>[[#Williams|Williams 2007, pp. 1550–1561: {{abbr|H|hydrogen}}, {{abbr|C|carbon}}, {{abbr|N|nitrogen}}, {{abbr|P|phosphorus}}, {{abbr|O|oxygen}}, {{abbr|S|sulfur}}]]</ref> bioelements,<ref>[[#Wächtershäuser|Wächtershäuser 2014, p. 5: {{abbr|H|hydrogen}}, {{abbr|C|carbon}}, {{abbr|N|nitrogen}}, {{abbr|P|phosphorus}}, {{abbr|O|oxygen}}, {{abbr|S|sulfur}}, {{abbr|Se|selenium}}]]</ref> central nonmetals,<ref>[[#Hengeveld|Hengeveld & Fedonkin 2007, pp. 181–226: {{abbr|C|carbon}}, {{abbr|N|nitrogen}}, {{abbr|P|phosphorus}}, {{abbr|O|oxygen}}, {{abbr|S|sulfur}}]]</ref> CHNOPS,<ref>[[#Wakeman|Wakeman 1899, p. 562]]</ref> essential elements,<ref>[[#Fraps|Fraps 1913, p. 11: {{abbr|H|hydrogen}}, {{abbr|C|carbon}}, {{abbr|Si|silicon}}, {{abbr|N|nitrogen}}, {{abbr|P|phosphorus}}, {{abbr|O|oxygen}}, {{abbr|S|sulfur}}, {{abbr|Cl|chlorine}}]]</ref> "non-metals",<ref>[[#Parameswaran|Parameswaran at al. 2020, p. 210: {{abbr|H|hydrogen}}, {{abbr|C|carbon}}, {{abbr|N|nitrogen}}, {{abbr|P|phosphorus}}, {{abbr|O|oxygen}}, {{abbr|S|sulfur}}, {{abbr|Se|selenium}}]]</ref>{{efn|The quote marks are not found in the source; they are used here to make it clear that the source employs the word ''non-metals'' as a formal term for the subset of chemical elements in question, rather than applying to nonmetals generally.}} orphan nonmetals,<ref>[[#Knight|Knight 2002, p. 148: {{abbr|H|hydrogen}}, {{abbr|C|carbon}}, {{abbr|N|nitrogen}}, {{abbr|P|phosphorus}}, {{abbr|O|oxygen}}, {{abbr|S|sulfur}}, {{abbr|Se|selenium}}]]</ref> or redox nonmetals.<ref>[[#Fraústo|Fraústo da Silva & Williams 2001, p. 500: {{abbr|H|hydrogen}}, {{abbr|C|carbon}}, {{abbr|N|nitrogen}}, {{abbr|O|oxygen}}, {{abbr|S|sulfur}}, {{abbr|Se|selenium}}]]</ref>}} The descriptive phrase ''unclassified nonmetals'' is used here for convenience.</div>

The elements in a fourth set are sometimes recognized as nonmetals:

<div style="margin-left:2em; text-indent:-2em;">
{{legend inline|#FC9A9B|size=110%}} the generally unreactive{{efn|"Crystalline boron is relatively inert."<ref>[[#Zhu2022|Zhu et al. 2022]]</ref> Silicon "is generally highly unreactive."<ref>[[#Graves|Graves 2022]]</ref> "Germanium is a relatively inert semimetal."<ref>[[#Rosenberg|Rosenberg 2013, p. 847]]</ref> "Pure arsenic is also relatively inert."<ref>[[#Obodovskiy|Obodovskiy 2015, p. 151]]</ref>{{efn|Arsenic is stable in dry air. Extended exposure in moist air results in the formation of a black surface coating. "Arsenic is not readily attacked by water, alkaline solutions or non-oxidizing acids".<ref>[[#Greenwood|Greenwood & Earnshaw 2002, p. 552]]</ref> It can occasionally be found in nature in an uncombined form.<ref>[[#Eagleson1994|Eagleson 1994, p. 91]]</ref> It has a positive standard reduction potential (As → As<sup>3+</sup> + 3e &#61; +0.30 V), corresponding to a classification of semi-noble metal.<ref>[[#Huang|Huang 2018, pp. 30, 32]]</ref>}} "Metallic antimony is&nbsp;… inert at room temperature."<ref>[[#Orisakwe|Orisakwe 2012, p. 000]]</ref> "Compared to {{abbr|S|sulfur}} and {{abbr|Se|selenium}}, {{abbr|Te|tellurium}} has relatively low chemical reactivity."<ref>[[#Yin|Yin et al. 2018, p. 2]]</ref>}}  metalloids,<ref name="Moeller">[[#Moeller1989|Moeller et al. 1989, p. 742]]</ref> sometimes considered a third category distinct from metals and nonmetals—boron, silicon, germanium, arsenic, antimony, tellurium.</div>
{{Quote box
|quote = While many of the early workers attempted to classify elements none of their classifications were satisfactory. They were divided into metals and nonmetals, but some were soon found to have properties of both. These were called metalloids. This only added to the confusion by making two indistinct divisions where one existed before.<ref>[[#Whiteford|Whiteford & Coffin 1939, p. 239]]</ref>
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|source = Whiteford & Coffin 1939, ''Essentials of College Chemistry''
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The boundaries between these types are not sharp.{{efn|Boundary fuzziness and overlaps often occur in classification schemes.<ref name="Jones"/>}} Carbon, phosphorus, selenium, and iodine border the metalloids and show some metallic character, [[#Hlike a metal|as does hydrogen]].

The greatest discrepancy between authors occurs in metalloid "frontier territory".<ref>[[#Russell|Russell & Lee 2005, p. 419]]</ref> Some consider metalloids distinct from both metals and nonmetals, while others classify them as nonmetals.<ref name="Goodrich etc">[[#Goodrich|Goodrich 1844, p. 264]]; [[#TheChemical1897|''The Chemical News'' 1897, p. 189]]; [[#Hampel|Hampel & Hawley 1976, pp. 174, 191]]; [[#Lewis|Lewis 1993, p. 835]]; [[#Hérold|Hérold 2006, pp. 149–50]]</ref> Some categorize certain metalloids as metals (e.g., arsenic and antimony due to their similarities to [[heavy metals]]).<ref>[[#Tyler|Tyler 1948, p. 105]]; [[#Reilly|Reilly 2002, pp. 5–6]]</ref>{{efn|Jones takes a philosophical or pragmatic view to these questions. He writes: "Though classification is an essential feature of all branches of science, there are always hard cases at the boundaries. The boundary of a class is rarely sharp{{nbsp}}... Scientists should not lose sleep over the hard cases. As long as a classification system is beneficial to economy of description, to structuring knowledge and to our understanding, and hard cases constitute a small minority, then keep it. If the system becomes less than useful, then scrap it and replace it with a system based on different shared characteristics."<ref name="Jones">[[#Jones|Jones 2010, pp. 169–71]]</ref>}} Metalloids resemble the elements universally considered "nonmetals" in having relatively low densities, high electronegativity, and similar chemical behavior.<ref name="Moeller"/>{{efn|For a related comparison of the [[properties of metals, metalloids, and nonmetals]], see [[#RDM|Rudakiya & Patel (2021), p. 36.]]}}

=== Noble gases ===
{{main|Noble gas}}
[[File:Argon ice 1.jpg|thumb|A small (about 2 cm long) piece of rapidly melting [[argon]] ice|alt=a glass tube, held upside down by some tongs, has a clear-looking ice-like plug in it which is slowly melting judging from the clear drops falling out of the open end of the tube]]
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 due to their exceptionally low [[chemical reactivity]].<ref name="Matson">[[#Matson|Matson & Orbaek 2013, p. 203]]</ref>

These elements exhibit similar properties, being colorlessness, odorless, and nonflammable. Due to their closed outer electron shells, noble gases possess weak [[interatomic force]]s of attraction, leading to exceptionally low melting and boiling points.<ref>[[#Jolly|Jolly 1966, p. 20]]</ref>

Chemically, the noble gases exhibit relatively high ionization energies, negligible or negative electron affinities, and high to very high electronegativities. The number of compounds formed by noble gases is in the hundreds and continues to expand,<ref>[[#Maosheng|Maosheng 2020, p. 962]]</ref> with most of these compounds involving the combination of oxygen or fluorine with either krypton, xenon, or radon.<ref>[[#Mazej|Mazej 2020]]</ref>

=== Halogen nonmetals ===
{{Main|Halogen}}Chemically, the halogen nonmetals have high ionization energies, electron affinities, and electronegativity values, and are relatively strong [[oxidizing agent]]s.<ref name="oxidizing">[[#Rudolph|Rudolph 1973, p. 133]]: "Oxygen and the halogens in particular{{nbsp}}... are therefore strong oxidizing agents."</ref> All four elements tend to form primarily [[ionic compound]]s with metals,<ref name="Cotton">[[#Cotton|Cotton et al. 1999, p. 554]]</ref> in contrast to the remaining nonmetals (except for oxygen) which tend to form primarily [[covalent compound]]s with metals.{{efn|Metal oxides are usually somewhat ionic, depending upon the metal element electropositivity.<ref>[[#Woodward|Woodward et al. 1999, pp. 133–194]]</ref> On the other hand, oxides of metals with high oxidation states are often either polymeric or covalent.<ref>[[#Phillips1965|Phillips & Williams 1965, pp. 478–479]]</ref> A polymeric oxide has a linked structure composed of multiple repeating units.<ref>[[#Moeller1989|Moeller et al. 1989, p. 314]]</ref>}}

=== Unclassified nonmetals ===
{{anchor|Unclassified nonmetal|right}}

[[File:Selenium black (cropped).jpg|thumb|right|[[Selenium]] conducts electricity around 1,000 times better [[photoconductor|when light falls on it]], a property used in [[Photodetector|light-sensing applications]].<ref>[[#Emsley2011|Emsley 2011, p. 478]]</ref>|alt=A small glass jar filled with small dull grey concave buttons. The pieces of selenium look like tiny mushrooms without their stems.]]

{{Anchor|Hlike a metal}}Hydrogen behaves in some respects like a metallic element and in others like a nonmetal.<ref>[[#Seese|Seese & Daub 1985, p. 65]]</ref> Like a metallic element it can, for example, form a [[solvation|solvated cation]] in [[aqueous solution]];<ref>[[#MacKay|MacKay, MacKay & Henderson 2002, pp. 209, 211]]</ref> it can substitute for [[alkali metal]]s in compounds such as the chlorides ([[sodium chloride|NaCl]] cf. [[hydrochloric acid|HCl]]) and nitrates ([[potassium nitrate|KNO<sub>3</sub>]] cf. [[nitric acid|HNO<sub>3</sub>]]), and in certain alkali metal [[organometallic chemistry|complexes]]<ref>[[#Cousins|Cousins, Davidson & García-Vivó 2013, pp. 11809–11811]]</ref><ref name="Cao4">[[#Cao|Cao et al. 2021, p. 4]]</ref> as a nonmetal.<ref>[[#Liptrot|Liptrot 1983, p. 161]]; [[#MD|Malone & Dolter 2008, p. 255]]</ref> It attains this configuration by forming a covalent or ionic bond<ref name="Wiberg255–257">[[#Wiberg|Wiberg 2001, pp. 255–257]]</ref> or by bonding as an ion to a lone pair of electrons.<ref>[[#Scott1962|Scott & Kanda 1962, p. 153]]</ref>

Some or all of these nonmetals share several properties. Being generally less reactive than the halogens,<ref>[[#Taylor|Taylor 1960, p. 316]]</ref> most of them can occur naturally in the environment.<ref name="Emsley"/> Collectively, their physical and chemical characteristics can be described as "moderately non-metallic".<ref name="Cao20">[[Nonmetal#Cao|Cao et al. 2021, p. 20]]</ref> When combined with metals, the unclassified nonmetals can form [[interstitial compound|interstitial]] or [[refractory]] compounds.<ref>[[#Mess|Messler 2011, p. 10]]</ref> They also exhibit a tendency to [[catenation|bond to themselves]], particularly in solid compounds.<ref>[[#King1994|King 1994, p. 1344]]; [[#Powell|Powell & Tims 1974, pp. 189–191]]; [[#Cao|Cao et al. 2021, pp. 20–21]]</ref> Additionally, [[Diagonal relationship|diagonal periodic table relationships]] among these nonmetals mirror similar relationships among the metalloids.<ref>[[#Vernon2020|Vernon 2020, pp. 221–223]]; [[#RaynerW|Rayner-Canham 2020, p. 216]]</ref>