Selenium
📷 In Your World
Selenium has a unique property: it's a photoconductor, meaning it conducts electricity better when light shines on it. This made it the key ingredient in early photocopiers and light meters. Today, it's used to make red-colored glass and as a component in some anti-dandruff shampoos. It's also an essential trace nutrient for humans, acting as an important antioxidant.
📖 The Discovery Story
Selenium was discovered in 1817 by Swedish chemist Jöns Jacob Berzelius. He found it as an impurity in the sulfuric acid being produced at his factory. Because it was found alongside tellurium (named after Tellus, the Roman goddess of the Earth), Berzelius named the new element "selenium" after Selene, the Greek goddess of the Moon.
📊 Properties at a Glance
| Phase at STP | Solid |
| Melting Point | 221 °C / 430 °F |
| Boiling Point | 685 °C / 1265 °F |
| Electron Configuration | [Ar] 3d¹⁰4s²4p⁴ |
| Abundance in Earth's Crust | 0.000005% |
⚠️ Safety & Handling
While selenium is an essential micronutrient, it is toxic in large doses. Chronic overexposure can lead to a condition called selenosis, with symptoms like hair loss, nail problems, and neurological damage. Burning selenium produces a distinctive smell of rotten radishes.