Heavy metals

Heavy metals are metals or chemical compounds containing metals with relatively high density, high atomic weights, or atomic numbers.

This might mean up to 96 out of the 118 known chemical elements. Mercury, lead and bismuth are examples. The term is widely used in science. They have a density of more than 5 g/cm³. All of them are denser than iron

The term is sometimes used for any toxic metal, or metalloid such as arsenic, regardless of density.

The term heavy metals includes chromium, cobalt, nickel, copper, zinc, arsenic, silver, gold, cadmium, antimony, mercury, thallium, tungsten, platinum and lead.

The heaviest metal by density is osmium. Although most heavy metals are toxic, not all of them are. For example, gold, which is one of the heaviest metals, is non-toxic and chemically inert in the body. Some gold compounds are toxic, however. More specific definitions of a heavy metal have been proposed but none is widely used.

Heavy metals are scarce in the Earth's crust because most have sunk into the Earth's core. Many are used in modern life. They are used, for example, in golf clubs, cars, antiseptics, self-cleaning ovens, plastics, solar panels, mobile phones, and particle accelerators.

Heavy Metals Media

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  In a cello (example shown above) or a viola the C-string sometimes incorporates tungsten; its high density permits a smaller diameter string and improves responsiveness.

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  The Statue of Liberty. A stainless steel alloy armature provides structural strength; a copper skin confers corrosion resistance.

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  Cerium(IV) oxide is used as a catalyst in self-cleaning ovens.

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  Neodymium sulfate (Nd2(SO4)3), used to colour glassware

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  The Topaz Solar Farm, in southern California, features nine million cadmium-tellurium photovoltaic modules covering an area of 25.6 square kilometres (9.9 square miles).

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  An X-ray tube with a rotating anode, typically a tungsten-rhenium alloy on a molybdenum core, backed with graphite

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  Chromium crystalsand 1 cm3 cube

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  Arsenic, sealed in acontainer to stop tarnishing

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  Cadmium barand 1 cm3 cube

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  Mercury beingpoured into a petri dish

References

• Kumar V, Abbas AK & Aster JC 2013, 'Environmental and nutritional diseases,' in V Kumar, AK Abbas & JC Aster (eds), Robbins basic pathology, 9th ed, Elsevier, Philadelphia, PA. ISBN 978-1-4377-1781-5
• Newman MC & Unger MA 2003. Fundamentals of ecotoxicology, 2nd ed. Lewis, Boca Raton, FL. ISBN 1566705983
• Sengupta AK 2002, 'Principles of heavy metals separation', in AK Sengupta (ed), Environmental separation of heavy metals: engineering processes, Lewis, Boca Raton, FL. ISBN 1566768845

Related pages

• Hyperaccumulator