All practice pages/Interatomic theory/Elements
Element 8, a nonmetal
The most abundant element in the Earth's crust, in the oceans and in your body, and the one that makes fire and breathing possible.
Period 2, group 16: the middle of the top stroke of the 7. The other nonmetals are tinted, and every cell opens its own article.
Six valence electrons, two short of eight. Two oxygen atoms share two pairs, a double bond, and both reach eight.
Nearly half of the Earth's crust by mass is oxygen, locked into silicate rock and sand. It is 21% of the air by volume, 89% of water by mass and about 65% of your body by mass. Almost all of the free O₂ in the air was put there by photosynthesis. Oxygen has a second elemental form, ozone, O₃: three atoms instead of two, made by lightning and by ultraviolet light high in the atmosphere.
Carl Wilhelm Scheele made it in 1771 or 1772 by heating mercury oxide and other compounds, and called it fire air. Joseph Priestley made it independently in 1774 and published first. Lavoisier named it oxygen, acid-former, in 1777 because he believed every acid contained it. He was wrong about that, but the name stuck.
Steelmaking, hospitals, welding torches and rocket engines use oxygen gas. In compounds it is everywhere: water, rock, glass, cement, and every carbohydrate, fat and protein in food.