Editing Metalloid (section)

===Near metalloids===
[[File:Iodinecrystals.JPG|thumb|right|[[Iodine]] crystals, showing a metallic [[lustre (mineralogy)|lustre]]. Iodine is a [[semiconductor]] in the direction of its planes, with a [[band gap]] of ~1.3&nbsp;eV. It has an [[electrical conductivity]] of 1.7 × 10<sup>−8</sup>&nbsp;S•cm<sup>−1</sup> at [[room temperature]].<ref>[[#Greenwood2002|Greenwood & Earnshaw 2002, p.&nbsp;804]]</ref> This is higher than selenium but lower than boron, the least electrically conducting of the recognised metalloids.{{refn|1=The separation between molecules in the layers of iodine (350&nbsp;pm) is much less than the separation between iodine layers (427&nbsp;pm; cf. twice the van der Waals radius of 430&nbsp;pm).<ref>[[#Greenwood2002|Greenwood & Earnshaw 2002, p.&nbsp;803]]</ref> This is thought to be caused by electronic interactions between the molecules in each layer of iodine, which in turn give rise to its semiconducting properties and shiny appearance.<ref>[[#Wiberg2001|Wiberg 2001, p.&nbsp;416]]</ref>|group=n}}|alt=Shiny violet-black coloured crystalline shards.]]
In the periodic table, some of the elements adjacent to the commonly recognised metalloids, although usually classified as either metals or nonmetals, are occasionally referred to as ''near-metalloids''<ref>[[#Craig2003|Craig & Maher 2003, p.&nbsp;391]]; [[#Schroers2013|Schroers 2013, p.&nbsp;32]]; [[#Vernon|Vernon 2013, pp.&nbsp;1704–05]]</ref> or noted for their metalloidal character. To the left of the metal–nonmetal dividing line, such elements include gallium,<ref>[[#Cotton1999|Cotton et al. 1999, p.&nbsp;42]]</ref> tin<ref>[[#Marezio|Marezio & Licci 2000, p.&nbsp;11]]</ref> and bismuth.<ref name=Vernon/> They show unusual packing structures,<ref>[[#Russell2005|Russell & Lee 2005, p.&nbsp;5]]</ref> marked covalent chemistry (molecular or polymeric),<ref>[[#Parish1977|Parish 1977, pp.&nbsp;178, 192–93]]</ref> and amphoterism.<ref>[[#Eggins1972|Eggins 1972, p.&nbsp;66]]; [[#Rayner2006|Rayner-Canham & Overton 2006, pp.&nbsp;29–30]]</ref> To the right of the dividing line are carbon,<ref>[[#Atkins2006|Atkins et al. 2006, pp.&nbsp;320–21]]; [[#Bailar1989|Bailar et al. 1989, pp.&nbsp;742–43]]</ref> phosphorus,<ref>[[#Rochow1966|Rochow 1966, p.&nbsp;7]]; [[#Taniguchi1984|Taniguchi et al. 1984, p.&nbsp;867]]: "...&nbsp;black phosphorus&nbsp;... [is] characterized by the wide valence bands with rather delocalized nature."; [[#Morita1986|Morita 1986, p.&nbsp;230]]; [[#Carmalt|Carmalt & Norman 1998, p.&nbsp;7]]: "Phosphorus&nbsp;... should therefore be expected to have some metalloid properties."; [[#Du2010|Du et al. 2010]]. Interlayer interactions in black phosphorus, which are attributed to van der Waals-Keesom forces, are thought to contribute to the smaller band gap of the bulk material (calculated 0.19&nbsp;eV; observed 0.3&nbsp;eV) as opposed to the larger band gap of a single layer (calculated ~0.75&nbsp;eV).</ref> selenium<ref>[[#Stuke1974|Stuke 1974, p.&nbsp;178]]; [[#Cotton1999|Cotton et al. 1999, p.&nbsp;501]]; [[#Craig2003|Craig & Maher 2003, p.&nbsp;391]]</ref> and iodine.<ref>[[#Steudel1977|Steudel 1977, p.&nbsp;240]]: "...&nbsp;considerable orbital overlap must exist, to form intermolecular, many-center&nbsp;... [sigma] bonds, spread through the layer and populated with delocalized electrons, reflected in the properties of iodine (lustre, color, moderate electrical conductivity)."; [[#Segal1989|Segal 1989, p.&nbsp;481]]: "Iodine exhibits some metallic properties&nbsp;..."</ref> They exhibit metallic lustre, semiconducting properties{{refn|1=For example: intermediate electrical conductivity;<ref name="Lutz 2011, p.&nbsp;17">[[#Lutz2011|Lutz et al. 2011, p.&nbsp;17]]</ref> a relatively narrow band gap;<ref>[[#Yacobi1990|Yacobi & Holt 1990, p.&nbsp;10]]; [[#Wiberg2001|Wiberg 2001, p.&nbsp;160]]</ref> light sensitivity.<ref name="Lutz 2011, p.&nbsp;17"/>|group=n}} and bonding or valence bands with delocalized character. This applies to their most thermodynamically stable forms under ambient conditions: carbon as graphite; phosphorus as black phosphorus;{{refn|1=White phosphorus is the least stable and most reactive form.<ref>[[#Greenwood2002|Greenwood & Earnshaw 2002, pp.&nbsp;479, 482]]</ref> It is also the most common, industrially important,<ref>[[#Eagleson1994|Eagleson 1994, p.&nbsp;820]]</ref> and easily reproducible allotrope, and for these three reasons is regarded as the standard state of the element.<ref>[[#Oxtoby2008|Oxtoby, Gillis & Campion 2008, p.&nbsp;508]]</ref>|group=n}} and selenium as grey selenium.