“Selene,” Albert Aublet, 1880, oil on canvas
7 February 2025
Selenium is a chemical element with atomic number 34 and the symbol Se. It can appear as a red powder; a vitreous, black solid; or a gray metallic solid. It is rarely found in nature in a pure form, found usually in metal sulfide ores where it takes the place of sulfur. It is a chalcogen, a group that includes oxygen, sulfur, and tellurium. Selenium is toxic, although trace amounts are necessary for life as we know it. It has a variety of uses in industry, including production of glass, brass alloys, batteries, solar cells, and photoconductors.
Selenium was discovered by Jöns Jacob Berzelius and Johan Gottlieb Gahn in 1817. Berzelius named the element after Selene, the Greek goddess of the moon, paralleling the naming of tellurium, which was named after the earth. When burned, selenium gives off an odor reminiscent of horseradish, a similar odor to that exuded by tellurium, leading the chemist to initially think he was dealing with a tellurium compound. Subsequent work convinced him that his initial assessment was incorrect. Berzelius announced the discovery in a series of letters sent to chemists throughout Europe, which were subsequently published in various scientific journals. Here is an extract of one of those letters, dated 27 January 1818:
Da das reine Tellurium diesen Geruch nicht verbreitet, weder im metallischen noch im oxydirten Zustande, so vermuthe ich, dass die Tellurerze etwas von diesem Stoffe enthalten möchten. Diese Vermuthung gab mir Veranlassung den neuen Stoff Selenium, vom griechischen Namen des Mondes, zu nennen. Die Vermuthung mag sich nun bestätigen oder nicht, so kann er doch diesen Namen behalten, weil er doch einen Namen braucht.
(Since pure tellurium does not give off this smell, either in the metallic or oxidized state, I suspect that the tellurium ores may contain some of this substance. This suspicion led me to name the new substance selenium, from the Greek name for the moon. Whether or not this suspicion is confirmed, it can still keep this name because it needs a name.)
Sources:
Berzelius, Jöns Jacob. “Ein neues mineralisches Alkali und ein neues Metall” (27 January 1818). Journal für Chemie und Physik, 21, 1817, 44–48 at 47–48. HathiTrust Digital Archive. (Berzelius’s letter is dated 1818, while the volume of the journal is dated 1817; presumably the 1817 volume was published late.)
Miśkowiec, Pawel. “Name Game: The Naming History of the Chemical Elements—Part 2—Turbulent Nineteenth Century.” Foundations of Chemistry. 8 December 2022. DOI: 10.1007/s10698-022-09451-w.
Oxford English Dictionary, second edition, 1989. s.v. selenium, n.
Image credit: Albert Aublet, 1880; photo by Sotheby’s, New York, 2007. Wikimedia Commons. Public domain image as a mechanical reproduction of a public domain work.