18 Facts About Heavy metals

Some heavy metals are either essential nutrients, or relatively harmless, but can be toxic in larger amounts or certain forms.

Six elements near the end of periods 4 to 7 sometimes considered metalloids are treated here as Heavy metals: they are germanium, arsenic, selenium, antimony, tellurium, and astatine .

Atomic numbers of heavy metals are generally given as greater than 20 ; sometimes this is capped at 92 .

In biochemistry, heavy metals are sometimes defined—on the basis of the Lewis acid behaviour of their ions in aqueous solution—as class B and borderline metals.

Class A Heavy metals, which tend to have low electronegativity and form bonds with large ionic character, are the alkali and alkaline earths, aluminium, the group 3 Heavy metals, and the lanthanides and actinides.

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Class B Heavy metals, which tend to have higher electronegativity and form bonds with considerable covalent character, are mainly the heavier transition and post-transition Heavy metals.

Borderline Heavy metals largely comprise the lighter transition and post-transition Heavy metals .

All Heavy metals discovered from then until 1809 had relatively high densities; their heaviness was regarded as a singularly distinguishing criterion.

Lithophile heavy metals are mainly f-block elements and the more reactive of the d-block elements.

At the time of the Earth's formation, and as the most noble of Heavy metals, gold sank into the core due to its tendency to form high-density metallic alloys.

Broadly speaking, and with some exceptions, lithophile heavy metals can be extracted from their ores by electrical or chemical treatments, while chalcophile heavy metals are obtained by roasting their sulphide ores to yield the corresponding oxides, and then heating these to obtain the raw metals.

The chalcophile platinum group Heavy metals mainly occur in small quantities with other chalcophile ores.

Some common uses of heavy metals depend on the general characteristics of metals such as electrical conductivity and reflectivity or the general characteristics of heavy metals such as density, strength, and durability.

Typical uses of heavy metals can be broadly grouped into the following six categories.

In mechanical engineering, heavy metals are used for ballast in boats, aeroplanes, and motor vehicles; or in balance weights on wheels and crankshafts, gyroscopes, and propellers, and centrifugal clutches, in situations requiring maximum weight in minimum space .

Denser materials absorb more radioactive emissions than lighter ones, heavy metals are useful for radiation shielding and to focus radiation beams in linear accelerators and radiotherapy applications.

Copper, zinc, silver, gold, or mercury are used in antiseptic formulations; small amounts of some heavy metals are used to control algal growth in, for example, cooling towers.

The high reflectivity of some heavy metals is important in the construction of mirrors, including precision astronomical instruments.