heavyelement

Heavyelement is a term used in chemistry and physics to describe chemical elements with relatively high atomic number and mass. There is no single universal cutoff; the label is context dependent. In many uses, heavyelements refer to elements beyond the light, abundant elements such as carbon, nitrogen, and oxygen, with emphasis on transuranic and superheavy species. Examples commonly cited include lead (Pb, Z=82), uranium (U, Z=92), and plutonium (Pu, Z=94).

Properties of heavyelements are diverse. They generally have large, complex electron shells and many are radioactive. They tend to be dense metals with wide ranges of oxidation states, especially in the lanthanide and actinide series. Because of relativistic effects on their electrons, their chemistry can differ markedly from lighter elements.

Occurrence and synthesis. Some heavyelements occur naturally in trace amounts, such as lead, thorium, and uranium. Most heavier elements (transuranics and beyond) are synthetic, produced in nuclear reactors or particle accelerators. The heaviest known elements are highly unstable, with half-lives ranging from milliseconds to hours, and production experiments often yield only a few atoms at a time.

Applications and safety. Heavyelements have uses in nuclear energy, medical isotopes, scientific instrumentation, and specialized materials research. They also pose safety challenges due to radioactivity, toxicity, and long-term environmental concerns. Handling is restricted to licensed facilities and requires strict regulatory controls.