Cerium

Some elements were discovered at the same time by different people! One such element is cerium, which was discovered in 1803 by Swedish chemists Jöns Jacob Berzelius and Wilhelm Hisinger, and almost simultaneously in Germany by chemist Martin Heinrich Klaproth.

Hisinger had found a strange rock on his father’s estate, which he initially suspected of containing the newly discovered element tungsten. When this turned out not to be the case, he brought the mineral to Berzelius and together they identified the new element. Berzelius and Hisinger named the new element cerium, after Ceres, a recently discovered asteroid (which had been named in turn after the Roman goddess of agriculture).

However, something of a controversy ensued when, a few months after Berzelius and Hisinger published a paper about their discovery, Klaproth published a paper in the same journal, claiming to have discovered the element. In the end, it was decided that Berzelius and Hisinger found the element first. But the discoveries happened near enough to each other that it is still impossible to talk about cerium’s history without mentioning Klaproth.

Cerium is a silvery metal that’s about as hard as silver. It is ductile, meaning that it can stretch without breaking. Because cerium is electropositive, tending to lose its electrons easily, it combusts rapidly, which is why the element has applications as a fire starter.

Cerium is one of two elements that make sparks when struck (the other is iron). For this reason, cerium is commonly used in lighters and fire starters.

During the Manhattan Project—the World War II-era effort concentrated at Los Alamos National Laboratory to create the world’s first atomic bomb—scientists used cerium to create crucibles for casting plutonium metal. Cerium continues to be an important part of nuclear energy research at the Lab today.

Today, automakers use cerium in catalytic converters, which make certain exhaust chemicals from motor vehicles less toxic. Cerium is also used in television screens, in LED lightbulbs, and in chromium plating, which helps make metal shiny! Cerium is used as a glass polish, too.

Cerium oxide is by far the most used cerium compound. It’s used for polishing things and for making glass colorless. Adding cerium to pigments can make the pigments less likely to fade.

Although cerium sulfide was used to make crucibles for casting plutonium during the Manhattan Project, the compound has been used rarely for this purpose since.

Cerium is a major component of mischmetal, an alloy that also contains other rare earth elements, and that is commonly used in lighters to make sparks.

In nature, you’ll find cerium in four stable (non-radioactive), isotopes: cerium-136, cerium-138, and cerium-142. Cerium-140 is by far the most common (around 88% of cerium is found in this isotope).

Thirty-five radioactive cerium isotopes have been observed. The longest-lived, cerium-144, has a half-life of 285 days. Most of the other radioisotopes have far shorter half-lives, often of less than 10 minutes.

Cerium(III) and cerium(IV) are the element’s two most common oxidation states. For this reason, cerium tends to be in one of these forms when it makes a compound with other elements.

Cerium is the most common of the lanthanide, or rare earth, elements. Despite the name of this group of elements, the rare earths aren’t really all that rare. In fact, cerium is only slightly less abundant in the Earth’s crust than copper. It’s much more abundant than lead and tin.

The rare earth elements are sufficiently alike that they’re difficult to separate from each other (although among lanthanides, cerium is the easiest to separate).

It wasn’t until 1875 that American chemists William Hillebrand and Thomas Norton isolated cerium metal for the first time.

Cerium can be found in many minerals, but commercially produced cerium comes from monazite and bastnäsite. Most cerium comes from the United States, Brazil, India, Sri Lanka, Australia, and China.