Origin and use of the term metalloid#1960–present

File:Paracelsus.jpg (1493–1541), German-Swiss physician, iatrochemist, philosopher, astrologer and commentator as to the nature and properties of metals. He referred to zinc and bismuth as 'bastard' copper, and 'bastard' tin, respectively.Partington 1961, p. 148 Portrait by Quentin Massys]]

Ancient conceptions of metals as solid, fusible and malleable substances can be found in Plato's Timaeus (c. 360 BCE) and Aristotle's Meteorology.Cornford 1937, pp. 249–50Obrist 1990, pp. 163–64

More sophisticated classification arrangements were proposed by Pseudo-Geber (in the Geber corpus, c. 1310), Paracelsus (De Natura Rerum libri nonem, 1525–6; and later works), Basil Valentine (Conclusiones, 1624), and Boerhaave (Elementa Chemiæ, 1733). They attempted to separate the more characteristic metals from substances having those characteristics to a lesser degree. Such substances included zinc, antimony, bismuth, stibnite, pyrite and galena. These were all then called semimetals or bastard metals.Paul 1865, p. 933Roscoe & Schorlemmer 1894, pp. 3–4Partington 1961, pp. 148, 192–193

In 1735 Brandt proposed to make the presence or absence of malleability the principle of this classification. On that basis he separated mercury from the metals. The same view was adopted by Vogel (1755, Institutiones Chemiæ) and Buffon (1785, Histoire Naturelle des Minéraux). In the interim, Braun had observed the solidification of mercury by cold in 1759–60. This was confirmed by Hutchins and Cavendish in 1783.Jungnickel & McCormmach 1996, p. 279–281 The malleability of mercury then became known, and it was included amongst the metals.

In 1789 FourcroyFourcroy, p. 380 highlighted the weakness of this distinction between metals and semimetals. He said it was evident from the fact that

:between the extreme malleability of gold and the singular fragility of arsenic, other metals presented only imperceptible gradations of this character, and because there was probably no greater difference between the malleability of gold and that of lead, which was considered to be a metal, than there was between lead and zinc, which was classed among semi-metals, while in the substances intermediate between zinc and arsenic the differences were slight.

This idea of a semimetal, as a brittle (and thereby imperfect)Craig 1849Roscoe & Schorlemmer 1894, pp. 1–2 metal, was gradually discarded after 1789 with the publication of Lavoisier's 'revolutionary' Strathern 2000, p. 239 Elementary Treatise on Chemistry.Roscoe & Schormlemmer 1894, p. 4{{#tag:ref|In its first seventeen years, Lavoisier's work was republished in twenty-three editions and six languages, and carried his 'new chemistry' across Europe and America.Salzberg 1991, p. 204|group=n}}

File:Jöns Jacob Berzelius.jpg (1779–1848), Swedish chemist who popularized the use of the word metalloid to refer to nonmetallic chemical elements]]

In 1808, Erman and Simon suggested using the term metalloid to refer to the newly discovered elements sodium and potassium.Erman and Simon (1808) [https://books.google.com/books?id=rZaZAAAAIAAJ&pg=PA347 "3. Dritter Bericht des Hrn. Prof. Erman und des Geh. Oberbauraths Simon über ihre gemeinschaftlichen Versuche"] (Third report of Prof. Erman and State Architect Simon on their joint experiments), Annalen der Physik, 28 (3) : 347-367. After studying the new metallic elements that Humphry Davy had isolated, physicist Paul Erman and architect Paul Ludwig Simon concluded that potassium and sodium didn't conform to the traditional criteria of metals and therefore should be classified as "metalloids". From p. 347: "Hierin liegt aber eine sehr grosse Schwierigkeit, weil veilleicht keine der bekannten Substanzen einen so hohen Grad von Oxydabilität besitzt, als diese beiden Metalloide, wie man sie wohl an füglichsten vor der Hand nennen sollte." (However, here lies a very great difficulty because perhaps none of the known substances possess so high a degree of oxidizability as these two metalloids, as one should perhaps call those [that are] most conveniently available.) These elements were lighter than water and many chemists did not regard them as proper metals. Erman and Simon's proposal may have been made '[in] an attempt to revive this old distinction between metals and substances resembling metals'.Tweney & Shirshov 1935 Their suggestion was ignored by the chemical community.Goldsmith 1982, p. 526

In 1811, Berzelius referred to nonmetallic elements as metalloids,Berzelius 1811, p. 258 in reference to their ability to form oxyanions.Partington 1964, p. 168Bache 1832, p. 250 A common oxyanion of sulfur, for example, is the sulfate ion SO{{su|b=4|p=2−}}. Many metals can do the same. Chromium, for instance, can form the chromate ion CrO{{su|b=4|p=2−}}. Berzelius' terminology was widely adopted although it was subsequently regarded by some commentators as counterintuitive, misapplied, incorrectGlinka 1959, p. 76 or invalid.Hérold 2006, pp. 149–150 In 1825, in a revised German edition of his Textbook of Chemistry,Partington 1964, pp. 145, 168Jorpes 1970, p. 95 Berzelius subdivided the metalloids into three classes. These were: constantly gaseous 'gazolyta' (hydrogen, nitrogen, oxygen); real metalloids (sulfur, phosphorus, carbon, boron, silicon); and salt-forming 'halogenia' (fluorine, chlorine, bromine, iodine).Berzelius 1825, p. 168

In 1844, Jackson gave the meaning of 'metalloid' as 'like metals, but wanting some of their properties.'Jackson 1844, p. 368 In 1845, in A dictionary of science, literature and art, Berzelius' classification of the elementary bodies was represented as: I. gazolytes; II. halogens; III. metalloids ('resemble the metals in certain aspects, but are in others widely different'); and IV. metals.Brande & Cauvin 1845, p. 223

In 1864, calling nonmetals 'metalloids' was still sanctioned 'by the best authorities'The Chemical News and Journal of Physical Science 1864 even though this did not always seem appropriate. The greater propriety of applying the word metalloid to other elements, such as arsenic, had been considered.

By as early as 1866 some authors were instead using the term nonmetal, rather than metalloid, to refer to nonmetallic elements.Oxford English Dictionary 1989, 'nonmetal' In 1875, Kemshead observed that the elements had been subdivided into two classes—'non-metals or metalloids, and metals.' He added that '[t]he former term, although not so convenient, because a compound word, is more correct, and is now universally employed.'Kemshead 1875, p. 13

In 1876, Tilden protested against, 'the [still] too common though illogical practice of giving the name metalloid to such bodies as oxygen, chlorine or fluorine'. He instead divided the elements into ('basigenic') true metals, metalloids ('imperfect metals') and ('oxigenic') nonmetals.Tilden 1876, pp. 171–3; 198. He listed as metalloids: H; Ti(?), Zr; V, Nb(?), Ta(?); Mo, W, U; As, Sb, Bi; and Te. Non-metals included B, C, Si and Se. Graphitic C and Si were however noted as furnishing the only examples among the non-metals of electric conductivity.

As late as 1888, classifying the elements into metals, metalloids, and nonmetals, rather than metals and metalloids, was still regarded as peculiar and potentially confusing.The Chemical News and Journal of Physical Science 1888

Beach, writing in 1911, explained it this way:Beach 1911

:Metalloid (Gr. "metal-like"), in chemistry, any nonmetallic element. There are 13, namely, sulfur, phosphorus, fluorin[e], chlorin[e], iodine, bromine, silicon, boron, carbon, nitrogen, hydrogen, oxygen, and selenium. The distinction between the metalloids and the metals is slight. The former, excepting selenium and phosphorus, do not have a "metallic" lustre; they are poorer conductors of heat and electricity, are generally not reflectors of light and not electropositive; that is, no metalloid fails of all these tests. The term seems to have been introduced into modern usage instead of nonmetals for the very reason that there is no hard and fast line between metals and nonmetals, so that "metal-like" or "resembling metals" is a better description of the class than the purely negative "nonmetals". Originally it was applied to the nonmetals which are solid at ordinary temperature.

In or around 1917, the Missouri Board of Pharmacy wroteMayo 1917, p. 55 that:

:A metal may be said to differ from a metalloid [that is, a nonmetal] in being an excellent conductor of heat and electricity, in reflecting light more or less powerfully and in being electropositive. A metalloid may possess one or more of these characters, but not all of them ... Iodine is most commonly given as an example of a metalloid because of its metallic appearance.

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|quote = We may notice that the distinction between metals and non-metals is not a sharply defined one—the one class shades off into the other. In the case of copper and carbon the balance of evidence is clear enough, but in some cases (e.g. arsenic) there is just about as much to be said on one side as on the other, and it is impossible to decided whether the element is a metal or non-metal. Such elements are often called metalloids.

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}}During the 1920s the two meanings of the word metalloid appeared to be undergoing a transition in popularity. Writing in A Dictionary of Chemical Terms, CouchCouch 1920, p. 128 defined 'metalloid' as an old, obsolescent term for 'nonmetal.' {{#tag:ref|Couch also commented that there was, 'no sharp line of demarcation between metals and nonmetals as many of the latter class possess some metallic properties' [italics added].|group=n}} In contrast, Webster's New International Dictionary noted that use of the term metalloid to refer to nonmetals was the norm. Its application to elements resembling the typical metals in some way only, such as arsenic, antimony and tellurium, was recorded merely on a 'sometimes' basis.Webster's New International Dictionary 1926 p. 1359

Use of the term metalloid subsequently underwent a period of great flux up to 1940. Consensus as to its application to intermediate or borderline elements did not occur until the ensuing years, between 1940 and 1960.

In 1947, Pauling included a reference to metalloids in his classicLundgren & Bensaude-Vincent 2000, p. 409 and influentialGreenberg 2007, p. 562 textbook, General chemistry: An introduction to descriptive chemistry and modern chemical theory. He described them as 'elements with intermediate properties ... occupy[ing] a diagonal region [on the periodic table], which includes boron, silicon, germanium, arsenic, antimony, tellurium, and polonium.'Pauling 1947, p. 65

In 1959 the International Union of Pure and Applied Chemistry (IUPAC) recommended that '[t]he word metalloid should not be used to denote nonmetals'IUPAC 1959, p. 10 although it was still being used in this sense (around that time) by, for example, the French.Friend 1953, p. 68

In 1969 the classicAmerican Institute of Chemists 1969, p. 485 and authoritativeAmerican Chemical Society California section 1969, p. 55 Hackh's Chemical Dictionary included entries for both 'metalloid' and 'semimetal'. The latter term was described as obsolete.Grant 1969, pp. 422, 604: 'metalloid.—(1) having the physical properties of metals and the chemical properties of nonmetals, e.g., As. (2) a nonmetal (incorrect usage) ... semimetal.—an element midway in properties between metals and nonmetals, as arsenic (obsolete).'

In 1970 IUPAC recommended abandoning the term metalloid because of its continuing inconsistent use in different languages. They suggested using the terms metal, semimetal and nonmetal instead.IUPAC 1971, p. 11 Despite this recommendation, use of the term 'metalloid' increased dramatically. Google Ngram Viewer showed a fourfold increase in the use of the word 'metalloid' (as compared to 'semimetal') in the American English corpus from 1972 to 1983. There was a sixfold increase in the British English corpus from 1976 to 1983. As at 2011, the difference in usage across the English corpus was around 4:1 in favour of 'metalloid'.Google Ngram, viewed 11 February 2011

The most recent IUPAC publications on chemical nomenclature (the "Red Book", 2005) IUPAC 2005 and terminology (the "Gold Book", 2006–) IUPAC 2006– do not include any recommendations as to the usage or non-usage of the terms metalloid or semimetal.{{#tag:ref|The "Gold Book" contains one reference to semimetals in the physics-based sense (see 'semiconductor-metal transition') and one reference in the chemistry based sense (see 'organometallic compounds'). The latter entry notes that 'traditional metals and semi-metals' can form such compounds, as can 'boron, silicon, arsenic and selenium'.|group=n}}

Use of the term semimetal when discussing the periodic table, rather than metalloid, has recently been discouraged. This is because the former term 'has a well defined and quite distinct meaning' in band structure,Atkins 2010 et al., p. 20 where a semimetal is an element or a compound where the highest occupied and lowest unoccupied bands overlap in terms of energy, but have different momenta. This often results in only a small number of charge carrierscharge,Lovett 1977, p. 3Wilson 1939, pp. 21–22 for instance the densities in the elemental semimetals carbon (as graphite, in the direction of its planes), arsenic, antimony and bismuth are 3{{e|18}} cm⁻³, 2 {{e|20}} cm⁻³, 5{{e|19}} cm⁻³ and 3{{e|17}} cm⁻³ respectively.Feng & Jin 2005, p. 324 In contrast, the room-temperature concentration of charge carriers in metals usually exceeds 10²² cm⁻³.Sólyom 2008, p. 91

References to 'metalloid' as being outdated have also been described as 'nonsense' noting that 'it accurately describes these weird in-between elements'.Gray 2010

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Category:Metalloids

Category:Etymologies