seleniums

Seleniums refers to the chemical element selenium and its related compounds. Selenium is a nonmetal with the symbol Se and atomic number 34. It is part of the chalcogen group and exists in several allotropes, the most common being gray crystalline selenium and red amorphous selenium. In nature it is present only in trace amounts in the Earth’s crust and is typically obtained as a byproduct of refining copper and other sulfide ores. It occurs in minerals as selenides and selenates and is also found in organic matter.

Biological and nutritional role is a key aspect of selenium. It is an essential micronutrient for many organisms, incorporated into selenoproteins as the amino acid selenocysteine. These proteins, including glutathione peroxidases, thioredoxin reductases, and deiodinases, participate in antioxidant defense and thyroid hormone metabolism. Adequate intake is important for health; deficiency can contribute to diseases in certain populations, while excess intake can cause selenosis.

Industrial and technological applications include its use in glassmaking to adjust color and refractive properties, in pigments and coatings, and in electronics and photocopying technologies. Historically, selenium-based materials were employed in early xerography and rectifiers, and it remains of interest in semiconductor research and certain solar cell technologies. It is also produced for nutritional supplements in some markets.

Safety and environment: selenium compounds can be toxic at high exposures, and improper handling or disposal can affect ecosystems. Natural isotope composition includes several stable isotopes, with additional radioisotopes produced for medical and industrial uses.

History: selenium was discovered in 1817 by Jöns Jakob Berzelius and named after Selene, the Moon goddess.