Selenium is a chemical element with the symbol Se and atomic number 34. It belongs to the chalcogen group on the periodic table, along with oxygen, sulfur, tellurium, and polonium. Selenium is a nonmetal[1] and has several important applications in various industries, including electronics, glass manufacturing, and agriculture.
Selenium is a trace element found in the Earth’s crust, usually in association with sulfur-containing ores such as copper, lead, and zinc ores. It is also present in small amounts in soil, water, and some living organisms. Selenium is primarily obtained as a byproduct during the refining of copper, lead, and nickel ores.
Selenium gets its name from the Greek word “selene,” which means “moon.” Selene was the Greek goddess of the moon. 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. Johan Gottlieb Gahn, a metallurgist, first isolated a substance in 1817 from the byproducts of lead chamber sulfuric acid production. He observed that this material had properties similar to sulfur. Jöns Jakob Berzelius continued the study of selenium. In 1818, he obtained samples of selenium from Gahn and conducted more extensive experiments.
Berzelius characterized selenium as a nonmetallic element and determined its atomic weight. He investigated its properties, such as its ability to react with acids and form compounds with metals. Berzelius also established the differences between selenium and tellurium[2], clarifying their distinct chemical identities. 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 device allowed speech patterns to be transmitted on a beam of light. Approximately 2,000 tons of selenium are extracted annually worldwide. ermany typically produces the most selenium each year, while China actually consumes the most for industrial purposes.The element was featured in the films “Ghostbusters” and “Evolution.”
It can also be produced by recovering selenium dioxide from flue dust generated during the smelting of copper sulfide ores. Selenium is a grayish nonmetal with a metallic luster. It exists in several allotropic forms, including amorphous red selenium, gray selenium, and crystalline black selenium.
Selenium is a relatively reactive element, readily combining with other elements to form compounds. It exhibits both nonmetallic and metalloid properties. Selenium is used in the manufacture of photovoltaic cells, rectifiers, and photocells. It has semiconducting properties and is a vital component in the production of thin-film solar cells. Selenium compounds are utilized in the production of red-colored glass and enamels. They can provide a deep red color to glassware and are also employed in the manufacturing of photocopier drums.
Selenium is an essential trace element for many living organisms, including humans. It is a key component of certain enzymes and plays a role in various biological processes. Selenium supplements are used to address selenium deficiencies and support overall health. Selenium is an important micronutrient for plant growth and animal nutrition. It is used in fertilizers to ensure adequate selenium levels in soil and is included in animal feed to prevent selenium deficiencies in livestock.
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.
Selenium is essential for human health, and it functions as a cofactor for several enzymes with antioxidant properties. It is important for thyroid function, immune system support, and DNA synthesis. While selenium is required in trace amounts, excessive intake can lead to toxicity. High levels of selenium can cause selenosis, a condition characterized by hair and nail brittleness, gastrointestinal disturbances, and neurological symptoms.
Footnotes
- Nonmetals are a group of elements on the periodic table characterized by their lower melting and boiling points, poor conductivity of heat and electricity, and non-metallic appearance. They are located on the upper-right side of the periodic table and exhibit properties distinct from metals. Nonmetals have higher electronegativity values, tend to gain or share electrons when bonding, and commonly form covalent compounds. They can exist as solids, liquids, or gases at room temperature and display a range of reactivity. Examples of nonmetals include hydrogen, carbon, nitrogen, oxygen, sulfur, and others. Understanding the properties and behavior of nonmetals is essential in various scientific disciplines, including chemistry, biology, and materials science. [Back]
- Tellurium is a chemical element with the symbol Te and atomic number 52. It is a brittle, silvery-white metalloid that belongs to the chalcogen group on the periodic table. Tellurium was discovered in 1782 by the Romanian chemist Franz-Joseph Müller von Reichenstein, who found it as a component of a gold ore. However, its elemental nature was established later in the 19th century by the Swedish chemist Jöns Jakob Berzelius and the German chemist Martin Heinrich Klaproth. Tellurium has unique properties, including semiconductor behavior, thermoelectric properties, and the ability to form compounds with metals and nonmetals. It finds applications in a variety of industries, such as solar cells, thermoelectric devices, and metallurgy. [Back]
Further Reading
Sources
- “16 Interesting Selenium Facts” (Updated on August 25, 2021) https://www.thoughtco.com/interesting-selenium-facts-609110
- “Selenium Facts” (2020) https://www.softschools.com/facts/periodic_table/selenium_facts/211/
- “16 Interesting Selenium Facts – It’s required for proper nutrition in many organisms, including humans” (Updated on August 25, 2021) https://www.thoughtco.com/interesting-selenium-facts-609110
- “Selenium” (Updated May 25, 2023) https://en.wikipedia.org/wiki/Selenium
- Royal Society of Chemistry (RSC) – Selenium: https://www.rsc.org/periodic-table/element/34/selenium
- Los Alamos National Laboratory – Selenium: https://periodic.lanl.gov/34.shtml
- U.S. Geological Survey (USGS) – Selenium Statistics and Information: https://www.usgs.gov/centers/nmic/selenium-statistics-and-information
- National Center for Biotechnology Information (NCBI) – Selenium in Human Health: https://pubmed.ncbi.nlm.nih.gov/24409980/
- University of Maryland Medical Center – Selenium: https://www.umm.edu/health/medical/altmed/supplement/selenium
