Editing Nonmetal (section)

===Chemical===
{{hatnote|See also {{slink||Chemical properties by element type}}}}
{|class="wikitable floatright" style="line-height: 1.3; font-size: 95%; margin-left:20px"
|+ Some general chemistry-based<br/>differences between metals and nonmetals<ref name="Kneen"/>
|-
! colspan=2 | Aspect !! Metals !! Nonmetals
|-
| colspan=2 |Reactivity<ref>[[#Weller|Weller et al. 2018, preface]]</ref>
| colspan=2 style="text-align: center"| Wide range: very reactive to noble
|-
| rowspan =2 | [[Oxide]]s || lower
| [[base (chemistry)|Basic]]
| rowspan =2 | [[Acid]]ic; never basic<ref name="ReferenceC">[[#Abbott|Abbott 1966, p. 18]]</ref>
|-
| higher || Increasingly acidic
|-
| colspan=2 |Compounds<br>with metals<ref>[[#Ganguly|Ganguly 2012, p. 1-1]]</ref>
| [[Alloy]]s
| [[Covalent bond|Covalent]] or [[Ionic compounds|Ionic]]
|-
| colspan=2 | [[Ionization energy]]<ref name="AylwardIE"/>
| Low to high
| Moderate to very high
|-
| colspan=2 | [[Electronegativity]]<ref name="AylwardEN"/>
| Low to high
| Moderate to very high
|}
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, H<sub>2</sub>O<ref>[[#Eagleson1994|Eagleson 1994, 1169]]</ref>) or neutral (like [[nitrous oxide]], N<sub>2</sub>O<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<sup>−</sup> → HCOO<sup>−</sup>);<ref>[[#House2013|House 2013, p. 427]]</ref> and in water, NO reacts with oxygen to form nitrous acid HNO<sub>2</sub> (4NO + O<sub>2</sub> + 2H<sub>2</sub>O → 4HNO<sub>2</sub>).<ref>[[#LewisRS|Lewis & Deen 1994, p. 568]]</ref>}}), but never basic.

They tend to gain electrons during chemical reactions, in contrast to metallic elements which tend to donate electrons. This behavior is related to the stability of [[electron configuration]]s in the noble gases, which have complete outer [[electron shell|shells]], empirically described by the [[Octet rule#Other rules|duet]] and [[octet rule]]s of thumb, more correctly explained in terms of [[valence bond theory]].<ref>[[#SmithDW|Smith 1990, pp. 177–189]]</ref>

The chemical differences between metals and nonmetals stem from variations in how strongly atoms attract and retain electrons. Across a period of the periodic table, the nuclear charge increases as more protons are added to the nucleus.<ref>[[#Young2018|Young et al. 2018, p. 753]]</ref> However, because the number of inner electron shells remains constant, the [[effective nuclear charge]] experienced by the outermost electrons also increases, pulling them closer to the nucleus. This leads to a corresponding reduction in atomic radius,<ref>[[#Brown et al.|Brown et al. 2014, p. 227]]</ref> and a greater tendency of these elements to gain electrons during chemical reactions, forming negatively charged ions.<ref>[[#Moore|Moore 2016]]; [[#Burford|Burford, Passmore & Sanders 1989, p. 54]]</ref> Nonmetals, which occupy the right-hand side of the periodic table, exemplify this behavior.

Nonmetals typically exhibit higher [[ionization energy|ionization energies]], [[electron affinity|electron affinities]], and [[standard electrode potential]]s than metals. 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.

The number of compounds formed by nonmetals is vast.<ref>[[#Brady|Brady & Senese 2009, p. 69]]</ref> The first 10 places in a "top 20" table of elements most frequently encountered in 895,501,834 compounds, as listed in the [[Chemical Abstracts Service]] register for November 2, 2021, were occupied by nonmetals. Hydrogen, carbon, oxygen, and nitrogen collectively appeared in most (80%) of compounds. Silicon, a metalloid, ranked 11th. The highest-rated metal, with an occurrence frequency of 0.14%, was iron, in 12th place.<ref>[[#CAS|Chemical Abstracts Service 2021]]</ref>