Lists of metalloids

This is a list of 194 sources that each list metalloids: elements classified as metalloids. The sources are listed in chronological order. Lists of metalloids differ since there is no rigorous definition of metalloid (or its occasional alias, 'semi-metal'). Individual lists share common ground, with variations occurring at the margins. The elements most often regarded as metalloids are boron, silicon, germanium, arsenic, antimony and tellurium.[n 1] Wikipedia generally categorises these six as metalloids, with the addition of astatine. Other sources may subtract from this list or add a varying number of other elements.

This is a dynamic list and may never be able to satisfy particular standards for completeness. You can help by expanding it with reliably sourced entries.

Overview

Elements recognized as metalloids
	13	14	15	16	17
2	B Boron	C Carbon	N Nitrogen	O Oxygen	F Fluorine
3	Al Aluminium	Si Silicon	P Phosphorus	S Sulfur	Cl Chlorine
4	Ga Gallium	Ge Germanium	As Arsenic	Se Selenium	Br Bromine
5	In Indium	Sn Tin	Sb Antimony	Te Tellurium	I Iodine
6	Tl Thallium	Pb Lead	Bi Bismuth	Po Polonium	At Astatine
Commonly recognized (93%): B, Si, Ge, As, Sb, Te   Irregularly recognized (44%): Po, At   Less commonly recognized (24%): Se   Rarely recognized (9%): C, Al   Arbitrary metal-nonmetal dividing line: between Be and B, Al and Si, Ge and As, Sb and Te, Po and At
Recognition status, as metalloids, of some elements in the p-block of the periodic table. Percentages are median appearance frequencies in the lists of metalloids.[n 2] The staircase-shaped line is a typical example of the arbitrary metal–nonmetal dividing line found on some periodic tables.

Element		Citations	Frequency
		in n = 194 publications	194 = 100%
Arsenic	As	191.5	99%
Tellurium	Te	190.5	98%
Germanium	Ge	184.5	95%
Silicon	Si	183.5	95%
Antimony	Sb	169.5	87%
Boron	B	166	86%
Polonium	Po	93.5	48%
Astatine	At	78	40%
Selenium	Se	46	24%
Aluminium	Al	18	9.3%
Carbon	C	16.5	8.5%
Bismuth	Bi	11.5	5.9%
Phosphorus	P	10	5.2%
Beryllium	Be	7.5	3.9%
Tin	Sn	5.5	2.8%
Sulfur	S	3	1.5%
Livermorium	Lv	3	1.5%
Iodine	I	2.5	1.3%
Flerovium	Fl	1	0.5%
Gallium	Ga	1	0.5%
Hydrogen	H	1	0.5%
Lead	Pb	1	0.5%
Moscovium	Mc	1	0.5%
Tennessine	Ts	1	0.5%

Chronological list

This table show which elements are included in each of 194 different lists of metalloids. A parenthesized symbol indicates an element whose inclusion in a particular metalloid list is qualified in some way by the author(s). The 'citations' rows show how many and what percentage of the authorities consider each element to be a metalloid, with qualified citations counted as one-half.

Citations as metalloid by element
Element		Arsenic	Tellu­rium	Germa­nium	Silicon	Anti­mony	Boron	Polo­nium	Asta­tine	Sele­nium	Alu­minium	Carbon	Bis­muth	Phos­phorus	Beryl­lium	Tin	Sulfur	Liver­morium	Iodine	Other	Total
		As	Te	Ge	Si	Sb	B	Po	At	Se	Al	C	Bi	P	Be	Sn	S	Lv	I		avg
Citations (194 = 100%)		191.5	190.5	184.5	183.5	169.5	166	93.5	78	46	18	16.5	11.5	10	7.5	5.5	3	3	2.5	6	7.15
		99%	98%	95%	95%	87%	86%	48%	40%	24%	9.3%	8.5%	5.9%	5.2%	3.9%	2.8%	1.5%	1.5%	1.3%	3.1%
Source	Yr
Simmons[1]	1947	As	Te			Sb				Se											4
Pauling[2]	1949	As	Te	Ge	Si	Sb	B	Po													7
Szabó & Lakatos[3]	1954	As	Te	Ge	Si	Sb	B	Po	At		Al				Be						10
Dull, Metcalfe & Williams[4]	1958	As	Te	Ge	Si	Sb	B	Po	At		Al										9
Frey[5]	1958	As	Te	Ge	Si	Sb	B	Po													7
Johnstone & Miller[6]	1960	As	Te	Ge	Si	Sb	B			Se		C		P							9
Edwards et al.[7]	1961	As	Te	Ge	Si	Sb	B			Se									I		8
Bond[8]	1962	As	Te	Ge	Si	Sb	B	Po													7
Swift & Schaefer[9]	1962	As		Ge	Si	Sb	B						Bi								6
Hoffman[10]	1963	As	Te	Ge	Si	Sb	B								Be						7
Nathans[11]	1963	As	Te	Ge	Si	Sb	B		At												7
Bailar, Moeller & Kleinberg[12]	1965	As	Te	Ge						Se											4
Selwood[13]	1965	As	Te	Ge	Si	Sb	B	Po	At		Al		Bi			Sn				Ga	12
Bassett et al.[14]	1966		Te	Ge	Si	Sb	B	Po			Al				Be						8
Hultgren[15]	1966	As	Te	Ge	Si	Sb				Se		C									7
Metcalfe, Williams & Castka[16]	1966	As	Te	Ge	Si	Sb	B	Po			(Al)										7.5
Rochow[17]	1966	As	Te	Ge	Si	Sb	B	(Po)	(At)	(Se)		(C)	(Bi)	(P)							9
Mahan[18]	1967	As	Te	Ge	Si		B														5
Paul, King & Farinholt[19]	1967	As	Te	Ge	Si	Sb				Se											6
Siebring[20]	1967	As	Te	Ge	Si	Sb	B	Po			Al										8
Cotton & Lynch[21]	1968	As	Te	Ge	Si	Sb	B		At	Se		C									9
Dunstan[22]	1968	As	Te	(Ge)		Sb		Po			Al		Bi		Be	Sn				Pb	7.5
Tyrell & Warren[23]	1968	As	Te	(Ge)	Si	(Sb)	B	(Po)	At	(Se)	(Al)	(C)		(P)					(I)		9.5
Williams, Embree & DeBey[24]	1968	As	Te	Ge	Si	Sb	B	Po			Al										8
Chedd[25]	1969	As	Te	Ge	Si	Sb	B	Po	At												8
Hägg[26]	1969	As	Te	Ge		Sb			At							Sn					6
Holum[27]	1969	As	Te	Ge	Si	Sb	B	Po	At		Al										9
Hunter[28]	1969	As	Te		Si	Sb				Se											5
Moody[29]	1969	As	Te	Ge	Si	Sb	B	Po	At		Al				Be						10
Dickerson, Gray & Haight[30]	1970	As	Te	Ge	Si	Sb	B														6
Hardwick & Knobler[31]	1970	As	Te	Ge	Si	Sb	B														6
Williams, Embree & DeBay[32]	1970	As	Te	Ge	Si	Sb	B	Po			Al				Be						9
Dickson[33]	1971	As	Te	Ge	Si	Sb		Po													6
Emsley[34]	1971	As	Te	Ge		Sb															4
Nitz & Dhonau[35]	1971	As	Te	Ge	Si	Sb	B	Po													7
Pimentel & Spratley[36]	1971	As	Te	Ge	Si	Sb	B	(Po)	(At)	Se		C									9
Barrow[37]	1972	As	Te	Ge	Si		B														5
Choppin & Johnsen[38]	1972	As	Te	Ge	Si	Sb	B			Se											7
Horvath[39]	1973	As	Te	Ge	Si	Sb	B	Po													7
Pascoe[40]	1973		Te	Ge	Si		B		At	Se		C		P							8
Seager & Stoker[41]	1973	As	Te	Ge	Si	Sb	B	Po	At		Al				Be						10
Allen & Keefer[42]	1974	As	Te	Ge	Si	Sb	B		At	Se											8
Andrews[43]	1974	As	Te		Si		B		At												5
Day & Johnson[44]	1974	As	Te	Ge	Si	Sb		Po	At												7
Dickson[45]	1974	As	Te	Ge	Si	Sb		Po	At												7
Duffy[46]	1974	As	Te	Ge		Sb				Se											5
Fuller[47]	1974	As	Te	Ge	Si		B			Se		C									7
Nordmann[48]	1974	As	Te	Ge	Si		B	Po	At	Se											8
O'Connor[49]	1974	As	Te	Ge	Si	Sb	B	Po													7
Rock & Gerhold[50]	1974	As	Te	Ge	Si	Sb	B	Po	At												8
Pauling & Pauling[51]	1975	As	Te	Ge	Si	Sb	B	Po													7
Hearst & Ifft[52]	1976	As	Te	Ge	Si	Sb	B			Se											7
Tyler Miller[53]	1976	As	Te	Ge	Si	Sb	B	Po	At		Al									H	10
Waser, Trueblood & Knobler[54]	1976	As	Te	Ge	Si	Sb	B	Po													7
Bloomfield[55]	1977	As	Te	Ge	Si	Sb	B	Po	At		Al										9
Ucko[56]	1977	As	Te	Ge	Si	Sb	B	Po	At		Al										9
Hill & Holman[57]	1978	As	Te	Ge	Si		B					(C)									5.5
Coxon, Fergusson & Phillips[58]	1980	As	Te	Ge	Si	(Sb)	B		At						(Be)						7
Warrena & Geballe[59]	1981	As	Te		Si		B		At	Se		C		P			S				9
Walters[60]	1982	As	Te	Ge	Si		B														5
Edwards & Sienko[61]	1983	As	Te	Ge		Sb		Po	(At)												5.5
Holtzclaw, Robinson & Nebergall[62]	1984	As	Te	Ge	Si	Sb	B	Po	At												8
Boikess & Edelson[63]	1985	As	Te	Ge	Si		B														5
Peters[64]	1986	As	Te	Ge	Si	Sb	B	Po	At												8
Hibbert & James[65]	1987	As	Te	Ge	Si	Sb		Po					Bi								7
Jones et al.[66]	1987	As	Te	Ge	Si	Sb	B	Po	At												8
McQuarrie & Rock[67]	1987	As	Te	Ge	Si	Sb	B	Po	At												8
Wulfsberg[68]	1987	As	Te	Ge	Si	Sb	B			Se											7
Thayer[69]	1988	As	Te	Ge	Si		B							P							6
Whitten, Gailey & Davis[70]	1988	As	Te	Ge	Si	Sb	B	Po	At		Al										9
Bailar et al.[71]	1989	As	Te	Ge	Si	Sb	B			Se											7
Gill[72]	1989	As	Te	Ge	Si	Sb	B														6
Malone[73]	1989	As	Te	Ge	Si	Sb	B	Po	At												8
Petrucci[74]	1989	As	Te	Ge	Si	Sb		Po	At												7
Puddephatt & Monaghan[75]	1989	As	Te	Ge	Si	Sb	B														6
Scott[76]	1989	As	Te	Ge	Si	Sb	B														6
Segal[77]	1989	As	Te	Ge	Si	Sb	B	Po													7
Oxtoby, Nachtrieb & Freeman[78]	1990	As	Te	Ge	Si	Sb	B	Po	At												8
Atkins & Beran[79]	1990	As	Te	Ge	Si	Sb		Po													6
Ebbing & Wrighton[80]	1993	As	Te	Ge	Si	Sb	B		At												7
Zumdahl[81]	1993	As	Te	Ge	Si	Sb	B	Po	At												8
Birk[82]	1994	As	Te	Ge	Si	Sb	B	Po													7
Smith[83]	1994	As	Te	Ge	Si	Sb	B														6
AAE[84]	1996	As	Te	Ge	Si	Sb	B			Se											7
Brady & Holum[85]	1996	As	Te	Ge	Si	Sb	B	Po	At												8
Harrison & de Mora[86]	1996	As	Te	Ge	Si		B														5
Hook & Post[87]	1996	As	Te	Ge	Si	Sb	B	Po	At												8
Atkins & Jones[88]	1997	As	Te	Ge	Si	Sb		Po													6
Dayah[89]	1997	As	Te	Ge	Si	Sb	B	Po													7
Mingos[90]	1998	As	Te	Ge	Si	Sb	B	Po													7
Joesten & Wood[91]	1999	As	Te	Ge	Si	Sb	B														6
Kremer[92]	1999	As	Te	Ge	Si	Sb	B														6
Thompson[93]	1999	As	Te	Ge	Si	Sb	B														6
Umland & Bellama[94]	1999	As	Te	Ge	Si		B		At	Se											7
Callister[95]	2000	As	Te	Ge	Si		B			Se		C									7
Enloe[96]	2000	As	Te		Si		B		At												5
Mann, Meek & Allen[97]	2000	As	Te	Ge	Si	Sb	B	Po					Bi								8
Phillips, Stozak & Wistrom[98]	2000	As	Te	Ge	Si	Sb	B	Po	At												8
Ryan[99]	2000	As	Te	Ge	Si		B														5
Hawkes[100]	2001	As	Te	Ge		Sb				Se			Bi								6
Lewis & Evans[101]	2001	As	Te	Ge	Si	Sb	B	Po													7
Masterton & Hurley[102]	2001	As	Te	Ge	Si	Sb	B														6
Barrett[103]	2002	(As)	(Te)	(Ge)	(Si)	(Sb)	(B)			(Se)											3.5
Chang[104]	2002	As	Te	Ge	Si	Sb	B	Po	At									Lv		Ts	10
Harding, Johnson & Janes[105]	2002	As	Te	Ge	Si	Sb															5
Johnson[106]	2002	As	Te	Ge	Si	Sb			At												6
Rodgers[107]	2002	As	Te	Ge	Si	Sb	B		At												7
Szefer[108]	2002	As	Te	Ge	Si	Sb				Se											6
Woodgate[109]	2002	As	Te	Ge		Sb					Al										5
Wright & Welbourn[110]	2002	As	Te	Ge	Si		B														5
e-encyclopedia[111]	2003	As	Te	Ge	Si	Sb	B			Se											7
Gupta[112]	2003	As	Te	Ge	Si	Sb	B														6
Hunt[113]	2003	As	Te	Ge	Si	Sb	B														6
Myers[114]	2003	As	Te	Ge	Si	Sb	B		At	Se											8
Williams[115]	2003	As	Te	Ge	Si	Sb	B	Po													7
Atkins[116]	2004	As	Te	Ge	Si	Sb	B	Po													7
Cox[117]	2004	As	Te	Ge	Si	Sb				Se											6
Gilbert, Kirss & Davies[118]	2004	As	Te	Ge	Si	Sb	B		At	Se											8
Reilly[119]	2004	As	Te	Ge	Si	Sb	B	Po	At	Se											9
Ebbing & Gammon[120]	2005	As	Te	Ge	Si	Sb	B		At												7
Fry & Page[121]	2005	As	Te	Ge	Si	Sb	B														6
Halliday, Resnick & Walker[122]	2005	As	Te	Ge	Si	Sb	B	Po	At												8
Holler & Selegue[123]	2005	As	Te	Ge	Si	Sb	B	Po	(At)												7.5
Kotz, Treichel & Weaver[124]	2005	As	Te	Ge	Si	Sb	B														6
Meyer[125]	2005	As	Te	Ge	Si	Sb	B		At												7
Orchin[126]	2005	As	Te	Ge	Si	Sb	B	Po	At												8
Swenson[127]	2005	As	Te	Ge	Si	Sb	B	Po	At	Se		C	Bi								11
Baird[128]	2006	As	Te	Ge	Si	Sb	B		At												7
Blei & Odian[129]	2006	As	Te	Ge	Si	Sb		Po	At									Lv			8
Brown & Holme[130]	2006	As	Te	Ge	Si	Sb	B		At												7
Dashek & Harrison[131]	2006	As	Te	Ge	Si	Sb	B	Po	At												8
Finch et al.[132]	2006	As	Te	Ge	Si	Sb	B			Se											7
Goldfrank & Flomenbaum[133]	2006	As	Te	Ge	Si	Sb	B		At												7
Hatt[134]	2006	As	Te	Ge	Si	Sb	B			Se											7
Hérold[135]	2006	As		Ge	Si		B	Po	(At)	Se		C	Bi	P							9.5
McMonagle[136]	2006	As	Te	Ge	Si		B											Lv		Fl Mc	8
Rayner-Canham & Overton[137]	2006	As	Te	Ge	Si		B														5
Silberberg[138]	2006	As	Te	Ge	Si	Sb	B														6
Slade[139]	2006	As	Te	Ge	Si	Sb	B	Po													7
Wertheim, Oxlade & Stockley[140]	2006	As	Te	Ge	Si	Sb	B		At	Se											8
Whitley[141]	2006	As	Te	Ge	Si	Sb	B	Po													7
American Chemical Society[142]	2007	As	Te	Ge	Si	Sb	B	Po													7
Astruc[143]	2007	As			Si		B			Se				P			S				6
Casper[144]	2007	As	Te	Ge	Si	Sb	B	Po													7
Crystal[145]	2007	As	Te	Ge	Si	Sb	B	Po													7
DeGraff[146]	2007	As	Te	Ge	Si	Sb	B	Po													7
Joesten, Hogg & Castellion[147]	2007	As	Te	Ge	Si	Sb	B														6
Lewis[148]	2007	As	Te	Ge	Si	Sb	B	Po		Se		C		P			S				11
Petty[149]	2007	As	Te	Ge	Si	Sb	B	Po	At	Se		C	Bi	P		Sn					13
Rösler, Harders & Bäker[150]	2007	As	Te	Ge	Si	Sb	B									(Sn)					6.5
Saunders[151]	2007	As	Te	Ge	Si	Sb	B	Po	At												8
Saunders[152]	2007	As	Te	Ge	Si	Sb	B	Po	At												8
Shipman, Wilson & Tood[153]	2007	As	Te	Ge	Si	Sb	B														6
Bauer, Birk & Sawyer[154]	2008	As	Te	Ge	Si	Sb	B		At												7
Clugston & Flemming[155]	2008	As	Te	Ge	Si	Sb				Se											6
Encyclopedia Columbia[156]	2008	As	Te			Sb				Se											4
Ham[157]	2008	As	Te	Ge	Si	Sb	B	Po													7
Kelter, Mosher & Scott[158]	2008	As	Te	Ge	Si	Sb	B		At												7
Masterton & Hurley[159]	2008	As	Te	Ge	Si	Sb	B														6
Merck[160]	2008	As	Te	Ge	Si	Sb	B	Po													7
Nicolaou & Montagnon[161]	2008	As	Te	Ge	Si	Sb	B	Po	At			C									9
Řezanka & Sigler[162]	2008	As	Te		Si		B		At	Se											6
Tro & Neu[163]	2008	As	Te	Ge	Si	Sb	B														6
Vallero[164]	2008	As	Te	Ge	Si	Sb	B	Po													7
Brown et al.[165]	2009	As	Te	Ge	Si	Sb	B														6
Burrows et al.[166]	2009	As	Te	Ge	Si	Sb	B			Se											7
Castor-Perry[167]	2009	As	Te	Ge	Si	Sb	B	Po	At										I		9
Cracolice & Peters[168]	2009	As	Te	Ge	Si	Sb	B		At												7
Economou[169]	2009	As	Te	Ge	Si	Sb	B	Po	At		Al										9
Habashi[170]	2009	As	Te	Ge	Si	Sb	B	Po		Se			Bi								9
Hein & Arena[171]	2009	As	Te	Ge	Si	Sb	B	Po													7
Leach[172]	2009	As	Te	Ge	Si	Sb	B	Po													7
Manning[173]	2009	As	Te	Ge	Si	Sb	B	Po													7
McMurray & Fay[174]	2009	As	Te	Ge	Si	Sb	B		At												7
Reger, Goode & Ball[175]	2009	As	Te	Ge	Si	Sb	B														6
Schnepp[176]	2009	As	Te	Ge	Si	Sb	B	Po	At												8
Shubert & Leyba[177]	2009	As	Te	Ge	Si	Sb	B														6
Whitten et al.[178]	2009	As	Te	Ge	Si	Sb	B		At												7
Aldinger & Weberruss[179]	2010	As	Te	Ge	Si	Sb	B														6
Banks et al.[180]	2010	As	Te	Ge	Si	Sb	B														6
Fayer[181]	2010	As	Te	Ge	Si	Sb	B	Po	At												8
Gray[182]	2010	As	Te	Ge	Si	Sb	B		At												7
Groysman[183]	2010	As	Te	Ge	Si	Sb		Po													6
Halka & Nordstrom[184]	2010	As	Te	Ge	Si	Sb	B	Po													7
Lombi E & Holm PE[185]	2010	As	Te	Ge	Si	Sb	B	Po	At												8
NEST Association[186]	2010	As	Te	Ge	Si	Sb	B		At												7
RCCS[187]	2010	As	Te	Ge	Si	Sb	B	Po	At	Se		C	Bi	P		Sn					13
Senese[188]	2010	As	Te	Ge	Si	Sb	(B)	Po	At	(Se)		C									9
Weiner[189]	2010	As	Te	Ge	Si	Sb	B	Po													7
Barbalace[190]	2011	As	Te	Ge	Si	Sb	B	Po													7
Encyclopædia Britannica Online[191]	2011	As	Te	Ge	Si	Sb	B	(Po)	(At)												7
Helmenstine[192]	2011	As	Te	Ge	Si	Sb	B	(Po)													6.5
Moore[193]	2011	As	Te	Ge	Si	Sb	B		At												7
QA International[194]	2011	As	Te	Ge	Si	Sb	B			Se											7
Element		Arsenic	Tellu­rium	Germa­nium	Silicon	Anti­mony	Boron	Polo­nium	Asta­tine	Sele­nium	Alu­minium	Carbon	Bis­muth	Phos­phorus	Beryl­lium	Tin	Sulfur	Liver­morium	Iodine	Other

• () Parenthesized symbols indicate elements whose inclusion in a particular metalloid list is qualified in some way by the author(s). It is counted as 0.5 citation.

There is an average of 7.15 elements per metalloid list.

Appearance frequency clusters

Clusters of elements and their appearance in the sources

Elements cited in the listed sources (as of August 2011; n = 194) have appearance frequencies that occur in clusters of comparable values. The diamonds in the graph mark the mean appearance frequency of each cluster. Cluster 1 (93%) = B, Si, Ge, As, Sb, Te; cluster 2 (44%) = Po, At; cluster 3 (24%) = Se; cluster 4 (9%) = C, Al; cluster 5 (5%) = Be, P, Bi; cluster 6 (3%) = Sn; and cluster 7 (1%) = H, Ga, S, I, Pb, Fl, Mc, Lv, Ts. The resulting geometric trend line has the formula y = 199.47e^−0.7423x and an R² value of 0.9962.[n 3]

Elements regarded as metalloids

The elements commonly classified as metalloids are boron, silicon, germanium, arsenic, antimony and tellurium.[n 4] The status of polonium and astatine is not settled. Most authors recognise one or the other, or both, as metalloids; Herman, Hoffmann and Ashcroft, on the basis of relativistic modelling, predict astatine will be a monatomic metal.[n 5] One or more of carbon, aluminium, phosphorus, selenium, tin or bismuth, these being periodic table neighbours of the elements commonly classified as metalloids, are sometimes recognised as metalloids.[n 6] Selenium, in particular, is commonly designated as a metalloid in environmental chemistry[n 7] on account of similarities in its aquatic chemistry with that of arsenic and antimony.[n 8] There are fewer references to beryllium, in spite of its periodic table position adjoining the dividing line between metals and nonmetals. Isolated references in the literature can also be found to the categorisation of other elements as metalloids. These elements include: hydrogen, nitrogen,[n 9] sulfur,[n 10] zinc,[n 11] gallium,[n 12] iodine,[n 13] lead,[n 14] and radon[n 15] (citations are for references other than those listed above).

Notes

1. Lack of a rigorous definition:
   • Goldsmith RH 1982, 'Metalloids', Journal of Chemical Education, vol. 59, no. 6, pp. 526–527, doi:10.1021/ed059p526
   • Hawkes SJ 2001, 'Semimetallicity', Journal of Chemical Education, vol. 78, no. 12, pp. 1686–87, doi:10.1021/ed078p1686
2. For a related commentary see also: Vernon RE 2013, 'Which Elements Are Metalloids?', Journal of Chemical Education, vol. 90, no. 12, pp. 1703–1707, doi:10.1021/ed3008457
3. The R² value is a measure of how close a formula fits a set of data points. Values fall between 0.0 and 1.0, with those near 1.0 indicating a good fit.
4. Elements commonly classified as metalloids:
   • Goldsmith RH 1982, 'Metalloids', Journal of Chemical Education, vol. 59, no. 6, pp. 526–7 (526), doi:10.1021/ed059p526
   • Mann JB, Meek TL & Allen LC 2000, 'Configuration energies of the main group elements', Journal of the American Chemical Society, vol. 122, no. 12, pp. 2780–3 (2783), doi:10.1021ja992866e: Mann et al. refer to these elements as 'the recognized metalloids'.
   • Kotz JC, Treichel P & Weaver GC 2009, Chemistry and Chemical Reactivity, 7th ed., Brooks/Cole, Belmont, California, ISBN 1439041318
5. Polonium and astatine:
   • Hawkes SJ 2001, 'Semimetallicity?', Journal of Chemical Education, vol. 78, no. 12, pp. 1686–87, doi:10.1021/ed078p1686
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   • Rochow EG 1966, The metalloids, DC Heath and Company, Boston, pp. 7–8
   • Cobb HM 2012, Dictionary of Metals, ASM International, Materials Park, OH, p. 145, ISBN 9781615039784
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   • Whiten K, Davis R, Peck L & Stanley G 2014, Chemistry, 10th ed., Brooks/Cole Cengage Learning, Belmont, CA, p. 134, ISBN 9781133610663
7. Selenium as a metalloid in environmental chemistry:
   • Meyer JS, Adams WJ, Brix KV, Luoma SM, Mount DR, Stubblefield WA & Wood CM (eds) 2005, Toxicity of dietborne metals to aquatic organisms, Proceedings from the Pellston Workshop on Toxicity of Dietborne Metals to Aquatic Organisms, 27 July – 1 August 2002, Fairmont Hot Springs, British Columbia, Canada, Society of Environmental Toxicology and Chemistry, Pensacola, Florida, p. 284, ISBN 1880611708
   • Weiner ER 2013, Applications of Environmental Aquatic Chemistry: A Practical Guide, 3rd ed., CRC Press, Boca Raton, FL, p. 181, ISBN 9781439853320
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   • US Environmental Protection Agency 1988, Ambient aquatic life water quality criteria for antimony (III), draft, Office of Research and Development, Environmental Research Laboratories, Washington, p. 1
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    • US Bureau of Naval Personnel 1965, Shipfitter 3 & 2, US Government Printing Office, Washington, p. 26
11. Zinc: Siebring BR 1967, Chemistry, MacMillan, New York, p. 613
12. Gallium: Wiberg N 2001, Inorganic chemistry, Academic Press, San Diego, p. 282, ISBN 0123526515
13. Iodine:
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14. Lead: Murray JF 1928, 'Cable-sheath corrosion', Electrical World, vol. 92, Dec 29, pp. 1295–7 (1295)
15. Radon:
    • Hampel CA & Hawley GG 1966, The encyclopedia of chemistry, 3rd ed., Van Nostrand Reinhold, New York,p. 950
    • Stein L 1985, 'New evidence that radon is a metalloid element: ion-exchange reactions of cationic radon', Journal of the Chemical Society, Chemical Communications, vol. 22, pp. 1631–2, doi:10.1039/C39850001631
    • Stein L 1987, 'Chemical properties of radon' in PK Hopke (ed.) 1987, Radon and its decay products: Occurrence, properties, and health effects, American Chemical Society, Washington DC, pp. 240–51 (240, 247–8), ISBN 0841210152

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