Introduction to Selenium
Imagine an element that changes its ability to conduct electricity just by sensing light! That’s Selenium (Se), a fascinating chemical element. It is a non-metal belonging to Group 16 of the periodic table, often found in different forms, like a red powder or a shiny grey solid. Selenium is considered a trace element, meaning living things need only very small amounts of it.
The Discovery of Selenium
The story of Selenium’s discovery takes place in 1817 in Sweden. A chemist named Jöns Jacob Berzelius was investigating a factory that produced sulfuric acid. He found a reddish-brown sediment during the process, which he initially mistook for Tellurium, another element. Upon further study, Berzelius realized it was a completely new element with its own unique properties. This marked the introduction of Selenium into the world of chemistry.
The Name’s Origin
Berzelius chose the name ‘Selenium’ because of its close relationship with Tellurium. ‘Tellus’ is the Latin word for Earth, and Tellurium had already been named after it due to its discovery in minerals from the Earth. Since Selenium was chemically similar to Tellurium and often found alongside it in nature, Berzelius decided to name the new element after the Earth’s companion in the sky: the Moon. In Greek mythology, ‘Selene’ is the goddess of the Moon. So, Selenium literally means ‘from the Moon’.
Quick Facts About Selenium
Here are some interesting facts about Selenium:
- Light Sensitivity: Selenium is a photoconductor, which means its electrical conductivity increases significantly when light shines on it. This property made it very useful in early photocopiers, photographic light meters, and solar cells.
- Colorful Allotropes: Selenium can exist in several distinct forms, called allotropes, each with different physical properties. One common form is a red amorphous (non-crystalline) powder, which can transform into a shiny, metallic grey, crystalline form when heated.
- Essential Trace Element: For humans and animals, Selenium is an essential trace element, necessary for various bodily functions, particularly in enzymes that protect cells from damage. It is found in some foods like nuts (e.g., Brazil nuts), grains, and seafood. In certain regions of India, the soil selenium levels can vary, influencing the selenium content in locally grown crops.
- Industrial Applications: Beyond electronics, Selenium is used in manufacturing ruby red glass and enamels, as a pigment, and in some rectifiers which convert alternating current to direct current.
- Natural Occurrence: Selenium is not typically found as a pure element in nature. Instead, it occurs in various minerals, often alongside sulfide ores of other metals like copper, lead, and silver, which are mined in different parts of the world, including regions with significant mineral deposits in India.