Editing Metalloid (section)

===Antimony===
{{Main|Antimony}}
[[File:Antimony-4.jpg|thumb|right|[[Antimony]], showing its brilliant [[lustre (mineralogy)|lustre]]|alt=A glistening silver rock-like chunk, with a blue tint, and roughly parallel furrows.]]
Antimony is a silver-white solid with a blue tint and a brilliant lustre.<ref name="Greenwood 2002, p. 552"/> It has a density of 6.697 g/cm<sup>3</sup> and is brittle, and moderately hard (more so than arsenic; less so than iron; about the same as copper).<ref name="GWM2011"/> It is stable in air and moisture at room temperature. It is attacked by concentrated nitric acid, yielding the hydrated pentoxide Sb<sub>2</sub>O<sub>5</sub>. [[Aqua regia]] gives the pentachloride SbCl<sub>5</sub> and hot concentrated sulfuric acid results in the [[antimony sulfate|sulfate]] Sb<sub>2</sub>(SO<sub>4</sub>)<sub>3</sub>.<ref name="Greenwood 2002, p. 553">[[#Greenwood2002|Greenwood & Earnshaw 2002, p.&nbsp;553]]</ref> It is not affected by molten alkali.<ref>[[#Dunstan1968|Dunstan 1968, p.&nbsp;433]]</ref> Antimony is capable of displacing hydrogen from water, when heated:  2 Sb + 3 H<sub>2</sub>O → Sb<sub>2</sub>O<sub>3</sub> + 3 H<sub>2</sub>.<ref>[[#Parise1996|Parise 1996, p.&nbsp;112]]</ref> It melts at 631&nbsp;°C. Antimony is a semimetal with an electrical conductivity of around 3.1 × 10<sup>4</sup>&nbsp;S•cm<sup>−1</sup><ref>[[#Carapella1968a|Carapella 1968a, p.&nbsp;23]]</ref> and a band overlap of 0.16&nbsp;eV.<ref name="Barfuß 1981, p. 967"/>{{refn|1=Antimony can also be prepared in an [[amorphous solid|amorphous]] semiconducting black form, with an estimated (temperature-dependent) band gap of 0.06–0.18&nbsp;eV.<ref>[[#Moss1952|Moss 1952, pp.&nbsp;174, 179]]</ref>|group=n}} Liquid antimony is a metallic conductor with an electrical conductivity of around 5.3 × 10<sup>4</sup>&nbsp;S•cm<sup>−1</sup>.<ref>[[#Dupree1982|Dupree, Kirby & Freyland 1982, p.&nbsp;604]]; [[#Mhiaoui2003|Mhiaoui, Sar, & Gasser 2003]]</ref>

Most of the chemistry of antimony is characteristic of a nonmetal.<ref>[[#Kotz2009|Kotz, Treichel & Weaver 2009, p.&nbsp;62]]</ref> Antimony has some definite cationic chemistry,<ref>[[#Cotton1999|Cotton et al. 1999, p.&nbsp;396]]</ref> SbO<sup>+</sup> and Sb(OH)<sub>2</sub><sup>+</sup> being present in acidic aqueous solution;<ref>[[#King1994|King 1994, p.&nbsp;174]]</ref>{{refn|1=Lidin<ref>[[#Lidin|Lidin 1996, p.&nbsp;372]]</ref> asserts that SbO<sup>+</sup> does not exist and that the stable form of Sb(III) in aqueous solution is an incomplete hydrocomplex [Sb(H<sub>2</sub>O)<sub>4</sub>(OH)<sub>2</sub>]<sup>+</sup>.|group=n}} the compound Sb<sub>8</sub>(GaCl<sub>4</sub>)<sub>2</sub>, which contains the homopolycation, Sb<sub>8</sub><sup>2+</sup>, was prepared in 2004.<ref>[[#Lindsjö|Lindsjö, Fischer & Kloo 2004]]</ref> It can form alloys with one or more metals such as aluminium,<ref>[[#Friend1953|Friend 1953, p.&nbsp;87]]</ref> iron, [[nickel]], copper, zinc, tin, lead, and bismuth.<ref>[[#Fesquet1872|Fesquet 1872, pp.&nbsp;109–14]]</ref> Antimony has fewer tendencies to anionic behaviour than ordinary nonmetals.<ref name=Cox/> Its solution chemistry is characterised by the formation of oxyanions.<ref name=Hiller225/> Like arsenic, antimony generally forms compounds in which it has an oxidation state of +3 or +5.<ref name=Massey267/> The halides, and the oxides and their derivatives are illustrative examples.<ref name=Bailar513/> The +5 state is less stable than the +3, but relatively easier to attain than with arsenic. This is explained by the poor shielding afforded the arsenic nucleus by its [[d electron count|3d<sup>10</sup> electrons]]. In comparison, the tendency of antimony (being a heavier atom) to [[redox|oxidize]] more easily partially offsets the effect of its 4d<sup>10</sup> shell.<ref>[[#Greenwood2002|Greenwood & Earnshaw 2002, p.&nbsp;553]]; [[#Massey2000|Massey 2000, p.&nbsp;269]]</ref> Tripositive antimony is amphoteric; [[penta-|pentapositive]] antimony is (predominately) acidic.<ref>[[#King1994|King 1994, p.&nbsp;171]]</ref> Consistent with an increase in metallic character down [[pnictogen|group 15]], antimony forms salts including an [[acetate]] Sb(CH<sub>3</sub>CO<sub>2</sub>)<sub>3</sub>, [[phosphate]] SbPO<sub>4</sub>, sulfate Sb<sub>2</sub>(SO<sub>4</sub>)<sub>3</sub> and [[perchlorate]] Sb(ClO<sub>4</sub>)<sub>3</sub>.<ref>[[#Turova2011|Turova 2011, p.&nbsp;46]]</ref> The otherwise acidic pentoxide Sb<sub>2</sub>O<sub>5</sub> shows some basic (metallic) behaviour in that it can be dissolved in very acidic solutions, with the formation of the [[oxycation]] SbO{{su|b=2|p=+}}.<ref>[[#Pourbaix1974|Pourbaix 1974, p.&nbsp;530]]</ref> The oxide Sb<sub>2</sub>O<sub>3</sub> is polymeric,<ref name=Pudd59/> amphoteric,<ref name="Wiberg2001p764">[[#Wiberg2001|Wiberg 2001, p.&nbsp;764]]</ref> and a glass former.<ref name=Rao22/> Antimony has an extensive organometallic chemistry (see [[Organoantimony chemistry]]).<ref>[[#House2008|House 2008, p.&nbsp;497]]</ref>