Selenium is a chemical element with symbol Se and atomic number 34. It is a nonmetal with properties that are intermediate between those of its periodic table column-adjacent chalcogen elements sulfur and tellurium. It rarely occurs in its elemental state in nature, or as pure ore compounds.
Three reasons Selenium stands out
- 1
Used in solar panels and shampoos.
- 2
It is an essential trace nutrient for humans, but the margin between a beneficial and a toxic dose is very narrow.
- 3
Brazil nuts are extraordinarily rich in it — just one nut can exceed the recommended daily intake.
The element that turns light into electricity
Selenium’s electrical conductivity increases under illumination, a response used in early photocopiers and light meters. Tiny amounts are nutritionally essential because selenium-containing enzymes protect cells. The safe range is narrow, however, and both deficiency and excess can cause harm.