This property has made selenium useful in devices that respond to the intensity of light, such as electric eyes, photo cells, light meters for cameras and copiers. Selenium can also produce electricity directly from sunlight and is used in solar cells.
Selenium is also a semiconductor and is used in some types of solid-state electronics as well as in rectifiers, devices which convert alternating current electricity into direct current electricity. In addition to its use in electrical devices, selenium is also used to make a ruby-red color in glasses and enamels, as a photographic toner and as an additive to stainless steel. Selenium forms few inorganic compounds, none of which are commercially important. Number of Stable Isotopes : 6 View all isotope data.
There is evidence 1 that selenoproteins reduce cancer risk by preventing cellular damage from radicals produced as by-products of oxygen metabolism, and they may also prevent, or slow, tumour growth by enhancing immune-cell activity.
In many countries, meat, seafood, rice, noodles and bread are common sources of dietary selenium, but ingesting too little or too much can have serious consequences. Selenium deficiency can cause heart disease or weaken the immune system, whereas excessive ingestion leads to selenosis selenium poisoning , with symptoms such as discoloration of the skin, a garlic odour to the breath and lack of mental alertness — more than 5 mg per day can be fatal.
Elemental selenium is usually assumed to be harmless, but many of its compounds, for example hydrogen selenide H 2 Se are extremely toxic. This is why the general perception is that selenium is toxic, even though modern science has recognized it as an essential micronutrient.
Recent advances indicate that selenium has the potential to improve human lives in varied ways, including as part of more efficient solar cells 2 , synthetic antioxidants 3 or nanocluster coatings for use in orthopaedic applications 4.
Combs, G. Jr BioFactors 14 , — Mayer, M. Article Google Scholar. Heverly-Coulson, G. Tran, P. CAS Google Scholar. Download references. You can also search for this author in PubMed Google Scholar. Correspondence to Russell Boyd. Reprints and Permissions. Boyd, R. Selenium stories. Nature Chem 3, Download citation. Amorphous selenium is either red, in powder form, or black, in vitreous, or glassy, form. The most stable form of the element, crystalline hexagonal selenium, is a metallic gray, while crystalline monoclinic selenium is a deep red.
The element resembles sulfur in its makeup. Here are the properties of selenium, according to the Jefferson Lab :. Berzelius also determined the atomics weights of many elements and developed a system of chemical symbols.
Berzelius discovered selenium after analyzing an impurity in sulfuric acid being produced at a factory in Sweden. He thought it was tellurium at first, and then realized it was unknown element, according to the Jefferson Lab. At one time, selenium was thought to be a toxin. In the s doctors began researching selenium's ability to fight tumors. It turns out both trains of thought were right. Some animal studies have shown that selenium may help protect against cancer, but that taking a supplement is not a good idea, according to the American Cancer Society.
There is very little room for error in dosage and just a little more than needed can be toxic. High doses can cause these side effects, according to the University of Maryland :. Selenium is found in many different foods.
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