Knowra Selenium Selenium Selenium is a chemical element with atomic number 34 and symbol Se. This nonmetal occurs in several forms and has electrical properties that change with light.
Periodic table : A tabular arrangement of chemical elements by atomic number, recurring chemical properties, and electron configuration. Selenium’s position among the chalcogens helps predict its properties.
Photoconductivity : An increase in a material’s electrical conductivity caused by absorbing light. Illumination raises the conductivity of certain selenium forms.
Photocopying : The reproduction of documents by forming an image through light-sensitive materials and electrostatic charge. Early xerographic machines used selenium photoconductors to form image patterns.
Selenium deficiency : A state in which selenium intake is insufficient to support normal biological functions. Low selenium can impair selenoprotein activity and contribute to specific disorders.
Jöns Jacob Berzelius : A Swedish chemist who helped establish modern chemical notation and discovered several elements. Berzelius identified selenium in 1817 while investigating residues from sulfuric acid production.
Chalcogen : An element in group 16 of the periodic table, including oxygen, sulfur, selenium, tellurium, and polonium. Selenium shares group chemistry with sulfur and tellurium.
Semiconductor : A material whose electrical conductivity lies between that of a conductor and an insulator and can be controlled. Selenium’s light-dependent electrical response is a semiconductor behavior.
Xerography : A dry copying process that uses electrostatic charges, light, and toner to reproduce images. Selenium’s photoconductivity helped make xerographic copying practical.
Selenosis : Illness caused by excessive exposure to selenium. The narrow margin between nutritional need and toxicity makes excess consequential.
Tellurium : A rare metalloid chemical element with atomic number 52 and symbol Te. Berzelius named selenium in relation to tellurium, whose name derives from Earth.
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