Seleeni

Seleeni is the Finnish name for the chemical element selenium (symbol Se, atomic number 34). Selenium is a nonmetal with semiconductor properties that occurs in several allotropes. In nature it is present only in trace amounts and is commonly obtained as a byproduct of the refining of copper and other sulfide ores. Industrially, selenium is used in glassmaking, pigments, electronics, and photocopiers, and it also has applications in photoelectric and rectifier devices.

In biology, selenium is an essential micronutrient for many organisms, including humans. It is incorporated into selenoproteins in the form of the amino acid selenocysteine, contributing to antioxidant defense, redox balance, and thyroid hormone metabolism. Dietary selenium requirements vary by age and geography; deficiency can contribute to heart and thyroid diseases, while excess intake can cause selenosis.

Occurrence and production: Selenium occurs naturally in soils and rocks; significant production occurs as a byproduct of copper refining and from other sulfide ore processing in several countries.

History and name: Discovered in 1817 by Jöns Jakob Berzelius, selenium was named after the Greek goddess Selene (the moon). The Finnish term seleeni is used in Finnish-language science and education to refer to the element.