Beyond Atomic Numbers - Every Element Has a Story
78.971
16
4
P Block
Non-metal
Selenium was discovered in 1817 by the Swedish chemist Jöns Jacob Berzelius while investigating impurities in sulfuric acid production. He named it after Selene, the Greek goddess of the Moon.
Selenium occurs in sulfide ores of copper, lead and nickel. It is mainly recovered as a by-product during copper refining.
Group 16 | Period 4 | P Block | Non-metal
Selenium is used in photocells, solar panels, photocopiers, glass manufacturing, pigments, electronics and nutritional supplements.
Sulfur, Tellurium, Copper and Silicon
Although essential in very small amounts, excessive selenium compounds can be toxic. Selenium also reacts with strong oxidizing agents.
Electronic Configuration: [Ar] 3d¹⁰ 4s² 4p⁴
Selenium's unique ability to conduct electricity better when exposed to light made it one of the first important photoconductive materials.
Before silicon became dominant, selenium was widely used in light-sensitive electronic devices and helped pave the way for modern photoelectric technology.
Selenium changes its electrical conductivity when exposed to light. This remarkable property made it valuable in early photocopiers, light meters and automatic doors.
Selenium is an essential micronutrient. It helps protect cells from oxidative damage and supports thyroid function, immunity and reproduction through important antioxidant enzymes.
Selenium has been used in photovoltaic devices that convert sunlight into electricity. Although modern solar panels mainly use silicon, selenium still plays an important role in specialized thin-film solar technologies.
For many years, selenium was the heart of photocopying machines because of its excellent photoconductive properties. Today, selenium compounds are also used in infrared optics, X-ray detectors, fiber-optic communication and advanced semiconductor devices.
Scientists are studying selenium nanomaterials for advanced electronics, renewable energy, medical imaging, drug delivery and environmental applications.
Selenium is produced during stellar nucleosynthesis inside massive stars and distributed across the universe by supernova explosions, eventually becoming part of planets and living organisms.
The element selenium is named after the Moon because it was discovered shortly after tellurium, whose name comes from the Latin word for Earth (Tellus).