All practice pages/Interatomic theory/Elements
Element 34, a nonmetal
Named for the moon, needed by your body in tiny amounts, and poisonous in slightly larger ones.
Period 4, group 16. The other nonmetals are tinted, and every cell opens its own article.
A nonmetal: it gains electrons to form negative ions with metals and shares them in covalent bonds with other nonmetals.
Rare, found with sulfur in copper and other sulfide ores, and nearly all of it is recovered during copper refining. Brazil nuts are especially rich in it.
Jöns Jacob Berzelius and Johan Gottlieb Gahn found it in 1817 in the red sludge of a sulfuric acid plant. Because it resembled tellurium, named for the Earth, Berzelius named it from the Greek selene, moon.
Glassmaking, to cancel the green tint iron gives glass or to make it red; producing manganese metal; thin-film solar cells; and anti-dandruff shampoo, which contains selenium sulfide. Its conductivity rises in light, which made it the heart of early photocopiers and light meters. It is also added to animal feed.
An essential nutrient in micrograms and toxic in milligrams. Hydrogen selenide gas is especially dangerous.