Heavy metals

  • a silvery thumbnail-size chunk of osmium with a highly irregular crystalline surface.
    crystals of osmium, a heavy metal
    nearly twice as dense as lead.[1]

    heavy metals are generally defined as metals with relatively high densities, atomic weights, or atomic numbers. the criteria used, and whether metalloids are included, vary depending on the author and context.[2] in metallurgy, for example, a heavy metal may be defined on the basis of density, whereas in physics the distinguishing criterion might be atomic number, while a chemist would likely be more concerned with chemical behaviour. more specific definitions have been published, but none of these have been widely accepted. the definitions surveyed in this article encompass up to 96 out of the 118 known chemical elements; only mercury, lead and bismuth meet all of them. despite this lack of agreement, the term (plural or singular) is widely used in science. a density of more than 5 g/cm3 is sometimes quoted as a commonly used criterion and is used in the body of this article.

    the earliest known metals—common metals such as iron, copper, and tin, and precious metals such as silver, gold, and platinum—are heavy metals. from 1809 onward, light metals, such as magnesium, aluminium, and titanium, were discovered, as well as less well-known heavy metals including gallium, thallium, and hafnium.

    some heavy metals are either essential nutrients (typically iron, cobalt, and zinc), or relatively harmless (such as ruthenium, silver, and indium), but can be toxic in larger amounts or certain forms. other heavy metals, such as cadmium, mercury, and lead, are highly poisonous. potential sources of heavy metal poisoning include mining, tailings, industrial wastes, agricultural runoff, occupational exposure, paints and treated timber.

    physical and chemical characterisations of heavy metals need to be treated with caution, as the metals involved are not always consistently defined. as well as being relatively dense, heavy metals tend to be less reactive than lighter metals and have far fewer soluble sulfides and hydroxides. while it is relatively easy to distinguish a heavy metal such as tungsten from a lighter metal such as sodium, a few heavy metals, such as zinc, mercury, and lead, have some of the characteristics of lighter metals, and, lighter metals such as beryllium, scandium, and titanium, have some of the characteristics of heavier metals.

    heavy metals are relatively scarce in the earth's crust but are present in many aspects of modern life. they are used in, for example, golf clubs, cars, antiseptics, self-cleaning ovens, plastics, solar panels, mobile phones, and particle accelerators.

  • definitions
  • origins and use of the term
  • biological role
  • toxicity
  • formation, abundance, occurrence, and extraction
  • properties compared with light metals
  • uses
  • notes
  • sources
  • further reading
  • external links

A silvery thumbnail-size chunk of osmium with a highly irregular crystalline surface.
Crystals of osmium, a heavy metal
nearly twice as dense as lead.[1]

Heavy metals are generally defined as metals with relatively high densities, atomic weights, or atomic numbers. The criteria used, and whether metalloids are included, vary depending on the author and context.[2] In metallurgy, for example, a heavy metal may be defined on the basis of density, whereas in physics the distinguishing criterion might be atomic number, while a chemist would likely be more concerned with chemical behaviour. More specific definitions have been published, but none of these have been widely accepted. The definitions surveyed in this article encompass up to 96 out of the 118 known chemical elements; only mercury, lead and bismuth meet all of them. Despite this lack of agreement, the term (plural or singular) is widely used in science. A density of more than 5 g/cm3 is sometimes quoted as a commonly used criterion and is used in the body of this article.

The earliest known metals—common metals such as iron, copper, and tin, and precious metals such as silver, gold, and platinum—are heavy metals. From 1809 onward, light metals, such as magnesium, aluminium, and titanium, were discovered, as well as less well-known heavy metals including gallium, thallium, and hafnium.

Some heavy metals are either essential nutrients (typically iron, cobalt, and zinc), or relatively harmless (such as ruthenium, silver, and indium), but can be toxic in larger amounts or certain forms. Other heavy metals, such as cadmium, mercury, and lead, are highly poisonous. Potential sources of heavy metal poisoning include mining, tailings, industrial wastes, agricultural runoff, occupational exposure, paints and treated timber.

Physical and chemical characterisations of heavy metals need to be treated with caution, as the metals involved are not always consistently defined. As well as being relatively dense, heavy metals tend to be less reactive than lighter metals and have far fewer soluble sulfides and hydroxides. While it is relatively easy to distinguish a heavy metal such as tungsten from a lighter metal such as sodium, a few heavy metals, such as zinc, mercury, and lead, have some of the characteristics of lighter metals, and, lighter metals such as beryllium, scandium, and titanium, have some of the characteristics of heavier metals.

Heavy metals are relatively scarce in the Earth's crust but are present in many aspects of modern life. They are used in, for example, golf clubs, cars, antiseptics, self-cleaning ovens, plastics, solar panels, mobile phones, and particle accelerators.

Other Languages
العربية: فلز ثقيل
azərbaycanca: Ağır metallar
বাংলা: ভারী ধাতু
башҡортса: Ауыр металдар
български: Тежки метали
bosanski: Teški metal
català: Metall pesant
čeština: Těžké kovy
dansk: Tungmetal
Deutsch: Schwermetalle
Ελληνικά: Βαρέα μέταλλα
español: Metal pesado
Esperanto: Pezmetalo
euskara: Metal astun
فارسی: فلز سنگین
galego: Metal pesado
한국어: 중금속
Bahasa Indonesia: Logam berat
íslenska: Þungmálmur
italiano: Metallo pesante
lietuvių: Sunkusis metalas
magyar: Nehézfém
Nederlands: Zwaar metaal
日本語: 重金属
norsk: Tungmetall
norsk nynorsk: Tungmetall
Plattdüütsch: Swoormetall
português: Metal pesado
română: Metale grele
Simple English: Heavy metals
slovenčina: Ťažký kov
slovenščina: Težka kovina
српски / srpski: Teški metal (hemija)
svenska: Tungmetall
Türkçe: Ağır metal
українська: Важкі метали
Tiếng Việt: Kim loại nặng
吴语: 重金属
粵語: 重金屬
中文: 重金属