cerium

Definition

A chemical element (symbol Ce) with an atomic number of 58, a very soft, ductile, silvery-white metal that tarnishes when exposed to air.

Etymology

From Ceres (“a recently discovered asteroid”) + -ium.

Example Sentences

• "Despite their name, rare earths are not so rare. The most common, cerium, is as plentiful in the Earth's crust as copper or lead. The difference between them and more familiar materials is that, in nature, rare earths are almost never found on their own. Rather, they're mixed with other minerals, and often at low concentrations, making them difficult to mine economically."