Berkelium

The first known discovery of berkelium happened in 1949 at the University of California, Berkeley. Stanley Thompson, Albert Ghiorso, and Glenn Seaborg bombarded americium with alpha particles (two protons and two neutrons, like helium without the electrons) for several hours in a 60-inch cyclotron—ultimately producing a new element. The isotope that they produced had a half-life of about five hours. It took another nine years before enough berkelium was made to see it with the naked eye (and the amount was only a few micrograms). It was named berkelium after Berkeley, California, the city of its discovery.

Berkelium is a soft, silvery-white, radioactive metal. It shares many qualities with the lanthanide terbium, it’s partner element in the lanthanide series. It is easily soluble in dilute mineral acids, and rapidly oxidizes in air or oxygen.

Because berkelium is rare, there are no commercial uses. However, it is used in scientific research as a target to synthesize heavier elements by charged particle bombardment. It has the lowest resistance to bulk compression of the actinides.

Berkelium forms two oxides, one a brown solid and the other a yellow-green solid. It also forms halides such as berkelium fluoride and berkelium chloride. Both of these are yellow green in appearance. Another halide is berkelium bromide, which has two forms. One is, you guessed it, yellow green. The other is just yellow.

Other inorganic compounds are berkelium sulfide and berkelium hydroxide. Berkelium sulfide is brownish black, while berkelium hydroxide shows a strong fluorescence when put under a green light. Berkelium also forms numerous alloys.

Berkelium metal exhibits two crystal forms: a double hexagonal close packed, and a face-centered cubic.

Nineteen isotopes of berkelium are now known and have been synthesized from mass number 233 to 253. All of the isotopes are radioactive. The half-lives range from 1,380 years (berkelium-247) to microseconds, therefore none could have persisted since Earth’s formation. Berkelium could have occurred naturally in the natural nuclear fission reactor in Oklo, Gabon, but would have long since decayed away. The isotope that is easiest to synthesize is berkelium-249, which is produced in nuclear reactors.

There are no natural sources of berkelium. It is artificially produced and only in small amounts. Most of the world’s berkelium is made at Oak Ridge National Laboratory in the High Flux Isotope Reactor, which was recently designated a Nuclear Historic Landmark.