Editing Metalloid (section)

===Germanium===
{{Main|Germanium}}
[[File:Polycrystalline-germanium.jpg|thumb|right|[[Germanium]] is sometimes described as a [[metal]]|alt=Greyish lustrous block with uneven cleaved surface.]]
Germanium is a shiny grey-white solid.<ref>[[#Greenwood2002|Greenwood & Earnshaw 2002, p.&nbsp;371]]</ref> It has a density of 5.323 g/cm<sup>3</sup> and is hard and brittle.<ref>[[#Cusack1967|Cusack 1967, p.&nbsp;193]]</ref> It is mostly unreactive at room temperature{{refn|1=Temperatures above 400&nbsp;°C are required to form a noticeable surface oxide layer.<ref>[[#Russell2005|Russell & Lee 2005, pp.&nbsp;399–400]]</ref>|group=n}} but is slowly attacked by hot concentrated [[sulfuric acid|sulfuric]] or [[nitric acid]].<ref name=Greenwood373>[[#Greenwood2002|Greenwood & Earnshaw 2002, p.&nbsp;373]]</ref> Germanium also reacts with molten [[sodium hydroxide|caustic soda]] to yield sodium germanate Na<sub>2</sub>GeO<sub>3</sub> and hydrogen gas.<ref>[[#Moody1991|Moody 1991, p.&nbsp;273]]</ref> It melts at 938&nbsp;°C. Germanium is a semiconductor with an electrical conductivity of around 2 × 10<sup>−2</sup>&nbsp;S•cm<sup>−1</sup><ref name=Greenwood373/> and a band gap of 0.67&nbsp;eV.<ref>[[#Russell2005|Russell & Lee 2005, p.&nbsp;399]]</ref> Liquid germanium is a metallic conductor, with an electrical conductivity similar to that of liquid mercury.<ref>[[#Berger1997|Berger 1997, pp.&nbsp;71–72]]</ref>

Most of the chemistry of germanium is characteristic of a nonmetal.<ref>[[#Jolly1966|Jolly 1966, pp.&nbsp;125–6]]</ref> Whether or not germanium forms a cation is unclear, aside from the reported existence of the Ge<sup>2+</sup> ion in a few esoteric compounds.{{refn|1=Sources mentioning germanium cations include: Powell & Brewer<ref>[[#Powell|Powell & Brewer 1938]]</ref> who state that the [[cadmium iodide]] CdI<sub>2</sub> structure of [[germanous iodide]] GeI<sub>2</sub> establishes the existence of the Ge<sup>++</sup> ion (the CdI<sub>2</sub> structure being found, according to Ladd,<ref>[[#Ladd|Ladd 1999, p.&nbsp;55]]</ref> in "many metallic halides, hydroxides, and chalcides"); Everest<ref>[[#Everest|Everest 1953, p.&nbsp;4120]]</ref> who comments that, "it seems probable that the Ge<sup>++</sup> ion can also occur in other crystalline germanous salts such as the [[germanous phosphite|phosphite]], which is similar to the salt-like [[stannous phosphite]] and [[germanous phosphate]], which resembles not only the stannous phosphates, but the [[manganous phosphate]]s also"; Pan, Fu & Huang<ref>[[#Pan|Pan, Fu and Huang 1964, p.&nbsp;182]]</ref> who presume the formation of the simple Ge<sup>++</sup> ion when Ge(OH)<sub>2</sub> is dissolved in a [[perchloric acid]] solution, on the basis that, "ClO4<sup>−</sup> has little tendency to enter [[coordination complex|complex]] formation with a cation"; Monconduit et al.<ref>[[#Monconduit|Monconduit et al. 1992]]</ref> who prepared the layer compound or phase Nb<sub>3</sub>Ge<sub>x</sub>Te<sub>6</sub> (x ≃ 0.9), and reported that this contained a Ge<sup>II</sup> cation; Richens<ref>[[#Richens|Richens 1997, p.&nbsp;152]]</ref> who records that, "Ge<sup>2+</sup> (aq) or possibly Ge(OH)<sup>+</sup>(aq) is said to exist in dilute air-free aqueous suspensions of the yellow hydrous monoxide…however both are unstable with respect to the ready formation of GeO<sub>2</sub>.''n''H<sub>2</sub>O"; Rupar et al.<ref>[[#Rupar|Rupar et al. 2008]]</ref> who synthesized a [[cryptand]] compound containing a Ge<sup>2+</sup> cation; and Schwietzer and Pesterfield<ref>[[#Schwietzer2010|Schwietzer & Pesterfield 2010, p.&nbsp;190]]</ref> who write that, "the monoxide [[GeO]] dissolves in dilute acids to give Ge<sup>+2</sup> and in dilute bases to produce GeO<sub>2</sub><sup>−2</sup>, all three entities being unstable in water". Sources dismissing germanium cations or further qualifying their presumed existence include: Jolly and Latimer<ref>[[#Jolly|Jolly & Latimer 1951, p.&nbsp;2]]</ref> who assert that, "the germanous ion cannot be studied directly because no germanium (II) species exists in any appreciable concentration in noncomplexing aqueous solutions"; Lidin<ref>[[#Lidin|Lidin 1996, p.&nbsp;140]]</ref> who says that, "[germanium] forms no aquacations"; Ladd<ref>[[#Ladd|Ladd 1999, p.&nbsp;56]]</ref> who notes that the CdI<sub>2</sub> structure is "intermediate in type between ionic and molecular compounds"; and Wiberg<ref>[[#Wiberg2001|Wiberg 2001, p.&nbsp;896]]</ref> who states that, "no germanium cations are known".|group=n}} It can form alloys with metals such as aluminium and [[gold]].<ref>[[#Schwartz2002|Schwartz 2002, p.&nbsp;269]]</ref> It shows fewer tendencies to anionic behaviour than ordinary nonmetals.<ref name=Cox/> Its solution chemistry is characterised by the formation of oxyanions.<ref name=Hiller225/> Germanium generally forms tetravalent (IV) compounds, and it can also form less stable divalent (II) compounds, in which it behaves more like a metal.<ref name="ReferenceC">[[#Eggins1972|Eggins 1972, p.&nbsp;66]]; [[#Wiberg2001|Wiberg 2001, p.&nbsp;895]]</ref> Germanium analogues of all of the major types of silicates have been prepared.<ref>[[#Greenwood2002|Greenwood & Earnshaw 2002, p.&nbsp;383]]</ref> The metallic character of germanium is also suggested by the formation of various [[oxoacid]] salts. A phosphate [(HPO<sub>4</sub>)<sub>2</sub>Ge·H<sub>2</sub>O] and highly stable trifluoroacetate Ge(OCOCF<sub>3</sub>)<sub>4</sub> have been described, as have Ge<sub>2</sub>(SO<sub>4</sub>)<sub>2</sub>, Ge(ClO<sub>4</sub>)<sub>4</sub> and GeH<sub>2</sub>(C<sub>2</sub>O<sub>4</sub>)<sub>3</sub>.<ref>[[#Glockling1969|Glockling 1969, p.&nbsp;38]]; [[#Wells1984|Wells 1984, p.&nbsp;1175]]</ref> The oxide GeO<sub>2</sub> is polymeric,<ref name=Pudd59/> amphoteric,<ref>[[#Cooper1968|Cooper 1968, pp.&nbsp;28–29]]</ref> and a glass former.<ref name=Rao22/> The dioxide is soluble in acidic solutions (the monoxide GeO, is even more so), and this is sometimes used to classify germanium as a metal.<ref>[[#Steele1966|Steele 1966, pp.&nbsp;178, 188–89]]</ref> Up to the 1930s germanium was considered to be a poorly conducting metal;<ref>[[#Haller 2006|Haller 2006, p.&nbsp;3]]</ref> it has occasionally been classified as a metal by later writers.<ref>[[#Walker|See, for example, Walker & Tarn 1990, p.&nbsp;590]]</ref> As with all the elements commonly recognised as metalloids, germanium has an established organometallic chemistry (see [[Organogermanium chemistry]]).<ref>[[#Wiberg2001|Wiberg 2001, p.&nbsp;742]]</ref>