Charges in transitions metals are variable - and only transition metals have unpaired electrons in their most common ionisation states. They form many different coloured ions and complexes. and changes in colour involve electronic changes of these complexes. When light passes through a solution containing transition metal complexes, we see those wavelengths of light that are transmitted. A colour wheel is a useful way show that the light that is absorbed by the metal is the complement of the light which is transmitted. i.e., the colour absorbed lies opposite the colour transmitted.

Semi conductor materials are defined in terms of band-gap. Diamond is a wide-band gap material, it is close to being an insulator and is colourless, unless they contain impurities. Silicon is black in colour, is a semi-conductor with a narrow band gap. Between these two are some medium-band-gap materials used as semi-conductors. These include coloured materials found in paint pigments such as cadmium yellow and vermilion.

Substance Mineral name Pigment name Band gap (eV) Colour
C Diamond - 5.4 Colourless
ZnO Zincite Zinc white 3.0 Colourless
CdS Greenockite Cadmium yellow 2.6 Yellow
HgS Cinnabar Vermilion 2.0 Red
HgS Metacinnabar - 1.6 Black
Si - - 1.1 Black
PbS Galena - 0.4 Black
Elements of the Periodic Table
Elementsort icon Atomic numbersort icon Atomic weightsort icon Boiling pointsort icon Densitysort icon Heat fusionsort icon Heat vapoursort icon Melting pointsort icon Specific heat capacitysort icon Thermal conductivitysort icon
Cadmium 48 112.4 1038.16° K 8650 kg/m³ 6.11 kJ/mol 100.08 kJ/mol 594.06° K 92.13 J/kg/K 14.6 W/m/K
Chromium 24 52 2938.16° K 7190 kg/m³ 13.82 kJ/mol 305.57 kJ/mol 2148.16° K 67 J/kg/K 7.8 W/m/K
Cobalt 27 58.93 3173.16° K 8900 kg/m³ 15.24 kJ/mol 389.45 kJ/mol 1768.16° K 67 J/kg/K 16 W/m/K
Copper 29 63.54 2868.16° K 8960 kg/m³ 13.02 kJ/mol 304.86 kJ/mol 1356.16° K 393.63 J/kg/K 59.3 W/m/K
Gold 79 196.97 3243.16° K 19300 kg/m³ 12.69 kJ/mol 342.55 kJ/mol 1336.16° K 297.32 J/kg/K 42 W/m/K
Hafnium 72 178.49 5673.16° K 13100 kg/m³ 21.78 kJ/mol 649.08 kJ/mol 2495.16° K 92.13 J/kg/K 3.1 W/m/K
Iridium 77 192.22 0 J/kg/K
Iron 26 55.85 3273.16° K 7860 kg/m³ 15.37 kJ/mol 354.27 kJ/mol 1809.16° K 75.38 J/kg/K 10 W/m/K
Manganese 25 54.94 2423.16° K 7430 kg/m³ 14.66 kJ/mol 224.87 kJ/mol 1518.16° K 5.4 W/m/K
Mercury Hg 80 200.59 630.16° K 13600 kg/m³ 2.35 kJ/mol 58.21 kJ/mol 234.76° K 8.38 J/kg/K 1.1 W/m/K
Molybdenum 42 95.94 5833.16° K 10200 kg/m³ 27.64 kJ/mol 536.01 kJ/mol 2883.16° K 146.57 J/kg/K 19 W/m/K
Nickel 28 58.71 3003.16° K 8900 kg/m³ 17.63 kJ/mol 381.07 kJ/mol 1726.16° K 92.13 J/kg/K 14.5 W/m/K
Niobium 41 92.91 3573.16° K 8400 kg/m³ 8 kJ/mol 26.8 kJ/mol 2741.16° K 52.35 J/kg/K
Osmium 76 190.2 5773.16° K 22600 kg/m³ 26.8 kJ/mol 678.39 kJ/mol 3273.16° K 0 J/kg/K 11 W/m/K
Palladium 46 106.4 4253.16° K 12000 kg/m³ 16.75 kJ/mol 376.88 kJ/mol 1825.16° K 9.3 W/m/K
Platinum 78 195.09 4803.16° K 21400 kg/m³ 19.68 kJ/mol 510.89 kJ/mol 2042.16° K 71.19 J/kg/K 9.5 W/m/K
Rhenium 75 186.2 6173.16° K 21000 kg/m³ 33.08 kJ/mol 636.52 kJ/mol 3453.16° K 71.19 J/kg/K 5.1 W/m/K
Rhodium 45 102.9 4773.16° K 12400 kg/m³ 21.78 kJ/mol 531.83 kJ/mol 2239.16° K 87.94 J/kg/K 22 W/m/K
Ruthenium 44 101.07 5173.16° K 12200 kg/m³ 25.54 kJ/mol 619.77 kJ/mol 2773.16° K 0 J/kg/K 10 W/m/K
Scandium 21 44.96 3003.16° K 3000 kg/m³ 15.91 kJ/mol 339.2 kJ/mol 1812.16° K 6.28 J/kg/K 1.5 W/m/K
Silver 47 107.87 2483.16° K 10500 kg/m³ 11.31 kJ/mol 254.19 kJ/mol 1233.96° K 410.39 J/kg/K 61.6 W/m/K
Tantalum 73 180.95 5698.16° K 16600 kg/m³ 28.48 kJ/mol 753.77 kJ/mol 3269.16° K 54.44 J/kg/K 8.1 W/m/K
Technetium 43 96.91
Titanium 22 47.9 3533.16° K 4510 kg/m³ 15.49 kJ/mol 445.98 kJ/mol 1941.16° K 2.4 W/m/K
Tungsten 74 183.85 6203.16° K 19300 kg/m³ 33.71 kJ/mol 774.71 kJ/mol 3683.16° K 167.5 J/kg/K 18.1 W/m/K
Vanadium 23 50.94 3723.16° K 6100 kg/m³ 17.59 kJ/mol 443.89 kJ/mol 2173.16° K 4 W/m/K
Yttrium 39 88.91
Zinc 30 65.37 1179.16° K 7140 kg/m³ 7.37 kJ/mol 114.74 kJ/mol 692.66° K 113.07 J/kg/K 16.7 W/m/K
Zirconium 40 91.22 3853.16° K 6490 kg/m³ 16.75 kJ/mol 502.51 kJ/mol 2125.16° K 2.4 W/m/K
Amazon Books
Image of Mendeleev on the Periodic Law: Selected Writings, 1869-1905
Author: Dmitri Ivanovich Mendeleev
Publisher: Dover Publications Inc. (2005)
Binding: Paperback, 320 pages