19 Interesting Selenium Facts

It's required for proper nutrition in many organisms, including humans

Brazil nuts in a wooden bowl
A Brazil nut has an adult's daily requirement of selenium.

Marat Musabirov / Getty Images

Selenium is a chemical element found in a wide variety of products. Here are some interesting facts about selenium:

  • Selenium gets its name from the Greek word "selene," which means "moon." Selene was the Greek goddess of the moon.
  • Selenium has atomic number 34, meaning each atom has 34 protons. The element symbol of selenium is Se.
  • Selenium was discovered jointly in 1817 by Swedish chemists Jöns Jakob Berzelius (1779–1848) and Johan Gottlieb Gahn (1745–1818).
  • Although it is uncommonly found, selenium does exist in relatively pure form, free in nature.
  • Selenium is a nonmetal. Like many nonmetals, it exhibits different colors and structures (allotropes) depending on the conditions.
  • Selenium is essential for proper nutrition in many organisms, including humans and other animals, but is toxic in larger amounts and in compounds.
  • Brazil nuts are high in selenium, even if they are grown in soil that is not rich in the element. A single nut provides enough selenium to meet the daily requirement for a human adult.
  • English electrical engineer Willoughby Smith (1828–1891) discovered that selenium reacts to light (photoelectric effect), leading to its use as a light sensor in the 1870s. Scottish-born American inventor Alexander Graham Bell (1847–1922) made a selenium-based photophone in 1879.
  • The primary use of selenium is to decolorize glass, to color glass red, and to make the pigment China Red. Other uses are in photocells, in laser printers and photocopiers, in steels, in semiconductors, and in assorted medicinal preparations.
  • There are six natural isotopes of selenium. One is radioactive, while the other five are stable. However, the half-life of the unstable isotope is so long that it is essentially stable. Another 23 unstable isotopes have been produced.
  • Selenium salts are used to help control dandruff.
  • Selenium is protective against mercury poisoning.
  • Some plants require high levels of selenium to survive, so the presence of those plants means the soil is rich in the element.
  • Liquid selenium exhibits extremely high surface tension.
  • Selenium and its compounds are anti-fungal.
  • Selenium is important to several enzymes, including antioxidant enzymes glutathione peroxidase and thioredoxin reductase and the deiodinase enzymes that convert thyroid hormones into other forms.
  • Approximately 2,000 tons of selenium are extracted annually worldwide.
  • Selenium is most commonly produced as a byproduct of copper refining.
  • The element was featured in the films "Ghostbusters" and "Evolution."