Green Lion Transition Metals
Charges in transitions metals are variable - and only transition metals have unpaired electrons in their most common ionisation states. Oxidation numbers also vary (oxidation numbers are not charges even though many times they can be the same as ionic charges). 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, what is seen is those wavelengths of light that are transmitted. A colour wheel as used by artists is another way to show that the light that is absorbed by a metal is the complement of the light which is transmitted i.e., the colour absorbed lies opposite the colour transmitted.
Transition metal compounds are typically used to make the phosphors in RGB monitors (a phosphor is a substance that exhibits the phenomenon of phosphorescence). An RGB monitor consists of a vacuum tube with three electron guns - one each for red, green and blue i.e. with separate signals for each of the three colours, and which fire electrons at a screen containing a phosphorous coating sensitive to the beams. Colour televisions use composite video signals, in which all the colours are mixed together. White light can be created by mixing three parts of the spectrum - the primary lights. The primary lights are those to which the eye is most sensitive and are predominant within the visible spectrum.
Artists recreate nature using the powdered colours of natural or artificial pigments. Pigments are the crystals found in paints used by artists, which when mixed result in darker colours and form the basis of the artist's palette of colours. In painting, complementary colours are mixed to create highlights and shadows. A colour wheel matches complementary colours and places them opposite each other.
As more is known about the elements new discoveries are incorporated into art; progressively cadmium and chromium colours, from the transition metals were discovered and added to the palette of the 19th Century artist. Cobalt compounds were used to produce a brilliant and permanent blue colour in ceramic glazes, glass, pottery, tiles, and enamels.