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References

1. Roher 2001, pp. 2‒3
2. Messler 2006, p. 347
3. Physical properties: "The lighter alkaline earths possess fairly high electrical and thermal conductivities and sufficient strength for structural use. The heavier elements are poor conductors and are too weak and reactive for structural use."[10] Chemical: The lighter alkaline earths show covalent bonding tendencies (Be predominantly; Mg considerably) whereas compounds of the heavier alkaline earths are predominantly ionic in nature; the heavier alkaline earths have more stable hydrides and less stable carbides.[11]
4. A first IUPAC definition states "[T]he elements of groups 3–12 are the d-block elements. These elements are also commonly referred to as the transition elements, though the elements of group 12 are not always included". Depending on the inclusion of group 12 as transition metals, the post-transition metals therefore may or may not include the group 12 elements—zinc, cadmium, and mercury. A second IUPAC definition for transition metals states "An element whose atom has an incomplete d sub-shell, or which can give rise to cations with an incomplete d sub-shell." Based on this definition one could argue group 12 should be split with mercury and probably also copernicium as transition metals, and zinc and cadmium as post-transition metals. Of relevance is the synthesis of mercury(IV) fluoride, which seemingly establishes mercury as a transition metal. This conclusion has been challenged by Jensen[12] with the argument that HgF4 only exists under highly atypical non-equilibrium conditions (at 4 K) and should best be considered as an exception. Copernicium has been predicted to have (a) an electron configuration similar to that of mercury; and (b) a predominance of its chemistry in the +4 state, and on that basis would be regarded as a transition metal. However, in recent years, doubt has been cast on the synthesis of HgF4 and the possible existence of copernicium(IV), so that group 12 would have only post-transition metals.
5. Jensen 2003, p. 952
6. Cox 2004, p. 17
7. Atkins & de Paula 2011, p. 352
8. Greenwood & Earnshaw 1998, pp. 222–3
9. Steele 1966, p. 193
10. Johnson 1970
11. The scandide contraction refers to the first row transition metals; the d-block contraction is a more general term.
12. Huheey & Huheey 1972, p. 229; Mason 1988
13. Cox 2004, pp. 20, 186, 188
14. Science Education 1948, p. 120
15. Deming 1940, p. 704–715
16. Moh's hardness values are taken from Samsanov,[22] unless otherwise noted; bulk coordination number values are taken from Darken and Gurry,[23] unless otherwise noted.
17. Russell & Lee 2005, p. 302
18. Steele 1966, p. 67
19. Deming 1940, pp. 705–7; Karamad, Tripkovic & Rossmeisl 2014
20. Cheemalapati, Keleher & Li 2008, p. 226
21. Liu & Pecht 2004, p. 54
22. Donohue 1982, p. 222
23. Vanderah 1992, p. 52
24. Lidin 1996, p. 110
25. Slabon et al. 2012
26. Larson et al. 2006, p. 035111-2
27. Schumann 2008, p. 52
28. Braunović 2014, p. 244
29. Donohue 1982, p. 222
30. Banthorpe, Gatforde & Hollebone 1968, p. 61; Dillard & Goldberg 1971, p. 558
31. Steiner & Campbell 1955, p. 394
32. Lidin 1996, p. 5
33. Klassen & Hoppe 1982; Darriet, Devalette & Lecart 1977; Sofin et al. 2002
34. Goodwin et al. 2005, p. 341
35. Köhler & Whangbo 2008
36. Arndt & Ganino 2012, p. 115
37. Goffer 2007, p. 176
38. Sidgwick 1950, p. 177
39. Pauling 1988, p. 698
40. Lidin 1996, p. 21–22
41. Miller et al. 2011, p. 150
42. Fishcher-Bünher 2011, p. 150
43. Smith 1990, p. 113
44. Sorensen 1991, p. 3
45. King 1995, pp.  xiii, 273–288; Cotton et al. 1999, pp. ix, 598; Massey 2000, pp. 159–176
46. The group 12 metals have been treated as transition metals for reasons of historical precedent, to compare and contrast properties, to preserve symmetry, or for basic teaching purposes.[53]
47. IUPAC 2005, p. 51
48. Crichton 2012, p. 11
49. The IUPAC Gold Book defines a transition metal as 'An element whose atom has an incomplete d sub-shell, or which can give rise to cations with an incomplete d sub-shell.[56]
50. Schweitzer 2003, p. 603
51. Hutchinson 1964, p. 562
52. Greenwood & Earnshaw 1998, p. 1209; Gupta CK 2002, p. 590
53. Rayner-Canham & Overton 2006, p. 30
54. Kneip 1996, p. xxii
55. Russell & Lee 2005, p. 339
56. Sequeira 2013, p. 243
57. Russell & Lee 2005, p. 349
58. Borsari 2005, p. 608
59. Dirkse 1986, pp. 287–288, 296; Ivanov-Emin, Misel'son & Greksa 1960
60. Wanamaker & Pennington 1921, p. 56
61. Rayner-Canham 2006, p. 570; Chambers & Holliday 1975, p. 58; Wiberg, Holleman & Wiberg 2001, p. 247; Aylward & Findlay 2008, p. 4
62. Francium may have a comparably low bonding energy but its melting point of around 8°C is significantly higher than that of mercury, at −39°C.
63. Poole 2004, p. 821
64. Mittemeijer 2010, p. 138
65. Russell & Lee 2005, pp. 1–2; 354
66. Rayner-Canham 2006, p. 567
67. Moeller 1952, pp. 859, 866
68. Cooney & Hall 1966, p. 2179
69. Mercury also forms partially anionic oxomercurates, such as Li2HgO2 and CdHgO4, by heating mixtures of HgO with the relevant cation oxides, including under oxygen pressure (Müller-Buschbaum 1995; Deiseroth 2004, pp. 173, 177, 185–186).
70. Deiseroth 2008, pp. 179‒180; Sevov 1993
71. Russell & Lee 2005, p. 354
72. Whitten et al. 2014, p. 1045
73. Cox 2004, p. 186
74. Kneen, Rogers & Simpson 2004, p. 370; Cox 2004, p. 199
75. Gerard & King 1968, p. 16; Dwight 1999, p. 2
76. Russell & Lee 2005, pp. 1–2; 359
77. The partially directional bonding in aluminium improves its shear strength but means that ultrahigh-purity aluminium cannot maintain work hardening at room temperature.[81]
78. Lyons 2004, p. 170
79. Cobb 2009, p. 323
80. Polemear 2006, p. 184
81. Without the use of thermal insulation and detailed structural design attention,[85] aluminium's low melting point and high thermal conductivity mitigate against its use, for example, in military ship construction—should a ship burn, the low melting point results in structural collapse; the high thermal conductivity helps spread the fire.[86] Its use in the construction of cargo ships is limited as little or no economic advantage is gained over steel, once the cost and weight of fitting thermal insulation is taken into account.[87]
82. Cooper 1968, p. 25; Henderson 2000, p. 5
83. Kauzlarich 2005, pp. 6009–10
84. Dennis & Such 1993, p. 391
85. Cramer & Covino 2006, p. 25
86. Aluminium can be attacked, for example, by alkaline detergents[92] (including those used in dishwashers);[93] by wet concrete,[94] and by highly acidic foods such as tomatoes, rhubarb or cabbage.[95] It is not attacked by nitric acid.[96]
87. Russell & Lee 2005, p. 360
88. See the list of metalloid lists for references
89. Clegg & Dovaston 2003, p. 5/5
90. Aluminium wire is used in electrical transmission lines for the distribution of power but, on account of its low breaking strength, is refinforced with a central core of galvanised steel wire.[99]
91. Kent 1993, pp. 13–14
92. Steele 1966, p. 60
93. In the absence of protective measures, the relatively high electropositivity of aluminium renders it susceptible to galvanic corrosion when in physical or electrical contact with other metals such as copper or steel, especially when exposed to saline media, such as sea water or wind-blown sea spray.[102]
94. Russell & Lee 2005, p. 387
95. Driess 2004, p. 151; Donohue 1982, p. 237
96. Walker, Enache & Newman 2013, p. 38
97. Atkins et al. 2006, p. 123
98. Corbett 1996, p. 161
99. Eranna 2012, p. 67
100. Chandler 1998, p. 59
101. Russell & Lee 2005, p. 389
102. Evans 1966, p. 129–130
103. Liang, King & White 1968, p. 288
104. Busev 1962, p. 33; Liang, King & White 1968, p. 287; Solov'eva et al. 1973, p. 43; Greenwood & Earnshaw 1998, p. 226; Leman & Barron 2005, p. 1522
105. Kneip 1996, p. xxii; Corbett 1996, pp. 153, 158
106. Russell & Lee 2005, p. 390
107. Wells 1985, p. 1279–80
108. Howe 1968a, p. 709; Taylor & Brothers 1993, p. 131; Lidin 1996, p. 410; Tóth & Győri 2005, pp. 4, 6–7
109. Chambers & Holliday 1975, p. 144
110. Bashilova & Khomutova 1984, p. 1546
111. Ropp 2012, p. 484
112. King & Schleyer 2004, p. 19
113. Corbett 1996, p. 153; King 2004, p. 199
114. Wiberg, Holleman & Wiberg 2001, p. 894
115. Haller 2006, p. 3
116. Russell & Lee 2005, p. 399
117. Ryan 1968, p. 65
118. Wiberg, Holleman & Wiberg 2001, p. 895
119. Abd-El-Aziz et al. 2003, p. 200
120. Cooper 1968, pp. 28–9
121. Ropp 2012, p. 405
122. Corbett 1996, p. 143
123. Russell & Lee 2005, p. 405
124. Charles, Crane and Furness write that, 'Most metals, except perhaps lead and tin, can be alloyed to give [yield] strengths that lie in the upper two-thirds of the low-strength range…'[133]
125. Rayner-Canham 2006, pp. 306, 340
126. Wiberg, Holleman & Wiberg 2001, p. 247
127. Corbett 1996, p. 143; Cotton et al. 1999, pp. 99, 122; Kauzlarich 2005, p. 6009
128. Russell & Lee 2005, pp. 402, 405
129. Russell & Lee 2005, p. 402, 407
130. Alhassan & Goodwin 2005, p. 532
131. Schweitzer 2003, p. 695
132. Mackay & Mackay 1989, p. 86; Norman 1997, p. 36
133. Hutchinson 1959, p. 455; Wells 1984, p. 1188; Liu, Knowles & Chang 1995, p. 125; Bharara & Atwood 2005, pp. 2, 4
134. Durrant & Durrant 1970, p. 670; Lister 1998, p. A12; Cox 2004, p. 204
135. Patnaik 2003, p. 474
136. Corbett 1996, pp. 143, 147; Cotton et al. 1999, p. 122; Kauzlarich 2005, p. 6009
137. Russell & Lee 2005, pp. 411, 13
138. As2O3 is usually regarded as being amphoteric but a few sources say it is (weakly)[147] acidic. They describe its "basic" properties (its reaction with concentrated hydrochloric acid to form arsenic trichloride) as being alcoholic, in analogy with the formation of covalent alkyl chlorides by covalent alcohols (e.g., R-OH + HCl → RCl + H2O)[148]
139. Russell & Lee 2005, p. 428
140. Eagleson 1994, p. 282
141. Russell & Lee 2005, p. 427
142. Sidgwick 1937, p. 181
143. Howe 1968, p. 62
144. Durrant & Durrant 1970, p. 790
145. Wiberg, Holleman & Wiberg 2001, p. 771; McQuarrie, Rock & Gallogly 2010, p. 111
146. Ropp 2012, p. 328
147. Miller, Lee & Choe 2002, p. 14; Aleandri & Bogdanović 2008, p. 326
148. Bobev & Sevov 2002
149. Xia & Bobev 2006
150. Bailar et al. 1984, p. 951
151. Which metal has the lowest electrical conductivity is debatable but bismuth is certainly in the lowest cohort; Hoffman[161] refers to bismuth as 'a poor metal, on the verge of being a semiconductor.'
152. Greenwood & Earnshaw 2002, pp. 781–3
153. Greenwood & Earnshaw 2002, pp. 762–5
154. Beamer & Maxwell 1946, pp.  1, 31
155. Russell & Lee 2005, p. 431
156. Halford 2006,p. 378
157. Legut, Friák & Šob 2010
158. Wiberg, Holleman & Wiberg 2001, pp. 594; Petrii 2012, p. 754
159. Bagnall 1966, p. 83
160. Bagnall 1966, pp. 42, 61; Wiberg, Holleman & Wiberg 2001, pp. 767–68
161. Schwietzer & Pesterfield pp. 241, 243
162. Bagnall[172] writes that the fusion of polonium dioxide with a potassium chlorate/hydroxide mixture yields a bluish solid which, '...presumably contains some potassium polonate.'
163. Wiberg, Holleman & Wiberg 2001, pp. 283, 595
164. Greenwood & Earnshaw 1998, p. 766
165. Bagnall[175] noted that the rare-earth polonides have the greatest thermal stability of any polonium compound.
166. Emsley 2011, p. 58
167. Hermann, Hoffmann & Ashcroft 2013, p. 11604–1
168. Hawkes 2010; Holt, Rinehart & Wilson c. 2007; Hawkes 1999, p. 14; Roza 2009, p. 12
169. Harding, Johnson & Janes 2002, p. 61
170. Merinis, Legoux & Bouissières 1972; Kugler & Keller 1985, pp. 110, 116, 210–211, 224; Takahashi & Otozai 1986; Zuckerman & Hagen 1989, pp. 21–22 (21); Takahashi, Yano & Baba 1992
171. Russell & Lee 2005, p. 299
172. Eberle1985, pp. 190, 192,
173. Brown et al. 2012, p. 264
174. Wiberg 2001, p. 283
175. Eagleson refers to the OH compound of astatine as hypoastatous acid HAtO;[185] Pimpentel and Spratley give the formula for hypoastatous acid as HOAt.[186]
176. Messler & Messler 2011, p. 38
177. Fine 1978, p. 718; Emsley 2011, p. 57
178. In hydrogen astatide the negative charge is predicted to be on the hydrogen atom,[189] implying that this compound should instead be referred to as astatine hydride (AtH).
179. Berei K & Vasáros 1985, p. 214
180. Pruszyński et al. 2006, pp. 91, 94
181. Zubieta & Zuckerman 2009, p. 260: 'The compounds AsSn and SbSn, which are classified as alloys of two B subgroup metals, exhibit superconducting properties with a transition temperature of about 4 K.'; Schwartz 2010, p. 32: 'The metals include the alkali and alkaline earths, beryllium, magnesium, copper, silver, gold and the transition metals. These metals exhibit those characteristics generally associated with the metallic state. The B subgroups comprise the remaining metallic elements. These elements exhibit complex structures and significant departures from typically metallic properties. Aluminum, although considered under the B subgroup metals, is somewhat anomalous as it exhibits many characteristics of a true metal.'
182. Greenwood and Earnshaw[193] refer to the B-subgroup metals as post-transition elements: 'Arsenic and antimony are classed as metalloids or semi-metals and bismuth is a typical B sub-group (post-transition-element) metal like tin and lead.'
183. Phillips & Williams 1965, pp. 4‒5; Steele 1966, p. 66
184. Phillips & Williams 1965, p. 33
185. Wiberg, Holleman & Wiberg 2001, pp. 1253, 1268
186. Steele 1966, p. 67
187. Harrington 1946, pp. 143, 146-147
188. Mingos 1998, pp. 18–19
189. Parish 1977, pp. 201–202
190. Aluminium is identified by Parish, along with germanium, antimony and bismuth, as being a metal on the boundary line between metals and non-metals; he suggests that all these elements are 'probably better classed as metalloids.'[201]
191. Rayner-Canham & Overton 2006, p. 29‒30
192. Pauling,[203] in contrast, refers to the strong metals in Groups 1 and 2 (that form ionic compounds with 'the strong nonmetals in the upper right corner of the periodic table.').
193. Vernon 2020
194. Rayner-Canham 2006, pp. 212 − 215
195. Russell & Lee 2005, p. 419
196. Cardarelli 2008, p. 1181
197. Louis 1911, p. 11–12
198. Van Wert 1936, pp. 16, 18
199. Britton, Abbatiello & Robins 1972, p. 704
200. Sargent-Welch 2008
201. Hawkes,[212] attempting to address the question of what is a heavy metal, commented that, 'Being a heavy metal has little to do with density, but rather concerns chemical properties'. He observed that, 'It may mean different things to different people, but as I have used, heard and interpreted the term over the last half-century, it refers to metals with insoluble sulfides and hydroxides, whose salts produce colored solutions in water, and whose complexes are usually colored.' He goes on to note that, 'The metals I have seen referred to as heavy metals comprise a block of all the metals in Groups 3 to 16 that are in periods 4 and greater. It may also be stated as the transition metals and post-transition metals.
202. Habashi 2010
203. Wiberg, Holleman & Wiberg 2001, p. 143
204. Klemm 1950
205. Miller GJ, Lee C & Choe W 2002, p. 22
206. Abrikosov 1988, p. 31
207. Cremer 1965, p. 514
208. Gray 2009, p. 9
209. Taylor et al. 2007, p. 148
210. Oxford English Dictionary 1989, 'other'
211. Roget's 21st Century Thesaurus
212. Gray 2010
213. Parish 1977, pp. 178, 189–190, 192–3
214. Slater 1939, p. 444‒445
215. On manganese, Slater says, '[It] is a very peculiar and anomalous exception to the general order of the elements. It is the only definite metal, far from the nonmetals in the table, which has a complicated structure.'[226]
216. Joshua 1991, p. 45
217. Farrell & Van Sicien 2007, p. 1442
218. Hill & Holman 2000, p. 40
219. Reid 2011, p. 143
220. Pashaey & Seleznev 1973, p. 565
221. Johansen & Mackintosh 1970, pp. 121–4; Divakar, Mohan & Singh 1984, p. 2337; Dávila et al. 2002, p. 035411-3
222. Jezequel & Thomas1997
223. Savitsky 1961, p. 107
224. Hindman 1968, p. 434: 'The high values obtained for the [electrical] resistivity indicate that the metallic properties of neptunium are closer to the semimetals than the true metals. This is also true for other metals in the actinide series.'; Dunlap et al. 1970, pp. 44, 46: '...α-Np is a semimetal, in which covalency effects are believed to also be of importance...For a semimetal having strong covalent bonding, like α-Np...'
225. Strathern 2000, p. 239
226. Roscoe & Schormlemmer 1894, p. 4
227. Murray 1809, p. 300
228. Young et al. 1969, p. 228
229. Cheronis, Parsons & Ronneberg 1942, p. 570
230. In fact, both aluminium (660.32) and germanium (938.25) have melting points greater than 425°C.
231. Subba Rao & Shafer 1979, p. 170
232. Collings 1986, p. 5
233. Temkin 2012, pp. 1, 726
234. Russell & Lee 2005, p. 165
235. Cotton et al. 1999, pp. 111–113; Greenwood & Earnshaw 2002, p. 111–113
236. Jensen 2008
237. Samsanov 1968
238. Darken & Gurry 1953, pp. 50–53
239. Young et al. 1969; Geffner 1969; Jensen 2003
240. IUPAC 2006–, transition element entry
241. Ogata, Li & Yip 2002; Russell & Lee 2005, p. 360; Glaeser 1992, p. 224
242. Holl 1989, p. 90
243. Ramroth 2006, p. 6; US Dept. of Transportation, Maritime Administration 1987, pp. 97, 358
244. Noble 1985, p. 21
245. Hinton & Dobrota 1978, p. 37
246. Holman & Stone 2001, p. 141
247. Hurd 2005, p. 4-15
248. Vargel 2004, p. 580
249. Hill & Holman 2000, p. 276
250. Liptrot 2001, p. 181
251. Davis 1999, p. 75–7
252. Charles, Crane & Furness 1997, pp. 49, 57
253. Wiberg 2001, pp. 750, 975; Silberberg 2006, p. 314
254. Sidgwick 1950, p. 784; Moody 1991, pp. 248–9, 319
255. Hoffman 2004
256. Bagnall 1962, p. 211
257. Bagnall 1966, p. 47
258. Eagleson 1994, p. 95
259. Pimpentel 1971, p. 827
260. Thayer 2010, p. 79
261. Greenwood & Earnshaw 1998, p. 548
262. Parish 1977, pp. 178
263. Pauling 1988, p. 173
264. Hawkes 1997
265. Slater 1939, p. 448