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t. e. Heavy metals are metallic elements with relatively high densities, atomic weights, or atomic numbers. The criteria used, and whether metalloids are included, vary depending on the author and context and has been argued should not be used. [2][3] A heavy metal may be defined on the basis of density, atomic number or chemical behaviour.
Toxic heavy metal. A 25-foot (7.6 m) wall of coal fly ash from the release of 5.4 million cubic yards ash slurry into the Emory River, Tennessee, in 2008. [1] The river water was contaminated with toxic metals including arsenic, copper, barium, cadmium, chromium, lead, mercury, nickel, and thallium. [2] Cleanup costs may exceed $1.2 billion.
An early use of the term heavy metal dates from 1817, when the German chemist Leopold Gmelin divided the elements into nonmetals, light metals, and heavy metals. Light metals had densities of 0.860–5.0 g/cm 3; heavy metals 5.308–22.000. The term later became associated with elements of high atomic weight or high atomic number.
Metal toxicity or metal poisoning is the toxic effect of certain metals in certain forms and doses on life. Some metals are toxic when they form poisonous soluble compounds. Certain metals have no biological role, i.e. are not essential minerals, or are toxic when in a certain form. [1] In the case of lead, any measurable amount may have ...
Arsenic is a notoriously toxic heavy metal. It occurs naturally in many minerals , usually in combination with sulfur and metals, but also as a pure elemental crystal . It has various allotropes , but only the grey form, which has a metallic appearance, is important to industry.
Cadmium. hexagonal close-packed (hcp) (hP2) Cadmium is a chemical element; it has symbol Cd and atomic number 48. This soft, silvery-white metal is chemically similar to the two other stable metals in group 12, zinc and mercury. Like zinc, it demonstrates oxidation state +2 in most of its compounds, and like mercury, it has a lower melting ...
samarium · lanthanum. neodymium. The rare-earth elements (REE), also called the rare-earth metals or rare earths or, in context, rare-earth oxides, and sometimes the lanthanides (although scandium and yttrium, which do not belong to this series, are usually included as rare earths), [1] are a set of 17 nearly indistinguishable lustrous silvery ...
A heavy, silvery d-block element, mercury is the only metallic element that is known to be liquid at standard temperature and pressure; [a] the only other element that is liquid under these conditions is the halogen bromine, though metals such as caesium, gallium, and rubidium melt just above room temperature. [b]