Heavy Metal (chemistry)
A heavy metal is a member of a loosely defined subset of elements that exhibit metallic properties. It mainly includes the transition metals, some metalloids, lanthanides, and actinides. Many different definitions have been proposed—some based on density, some on atomic number or atomic weight, and some on chemical properties or toxicity. The term heavy metal has been called a "misinterpretation" in an IUPAC technical report due to the contradictory definitions and its lack of a "coherent scientific basis". There is an alternative term toxic metal, for which no consensus of exact definition exists either. As discussed below, depending on context, heavy metal can include elements lighter than carbon and can exclude some of the heaviest metals. Heavy metals occur naturally in the ecosystem with large variations in concentration. In modern times, anthropogenic sources of heavy metals, i.e. pollution, have been introduced to the ecosystem. Waste-derived fuels are especially prone to contain heavy metals, so heavy metals are a concern in consideration of waste as fuel.
Other articles related to "heavy, metals":
... in gigawatt-days per metric ton of heavymetal, where heavymetal means actinides like thorium, uranium, plutonium, etc ... does not include elements such as oxygen that may be bonded to the fuel metals or cladding materials such as zirconium, which might be considered heavymetals by ...
Famous quotes containing the words heavy and/or metal:
“The Powers whose name and shape no living creature knows
Have pulled the Immortal Rose;
And though the Seven Lights bowed in their dance and wept,
The Polar Dragon slept,
His heavy rings uncoiled from glimmering deep to deep....”
—William Butler Yeats (18651939)
“There were metal detectors on the staff-room doors and Hernandez usually had a drawer full of push-daggers, nunchuks, stun-guns, knucks, boot-knives, and whatever else the detectors had picked up. Like Friday morning at a South Miami high school.”
—William Gibson (b. 1948)