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.