The chemical symbol for oxygen is O. Ordinary oxygen makes up approximately 20 percent of our atmosphere, and its chemical element is 02, because it is comprised of two oxygen atoms fused together.
Plants make oxygen. During the process of photosynthesis, oxygen is produced as a byproduct.
One of the most plentiful elements is oxygen. It makes up about a fifth of the air's volume. It can be found in the earth's crust and in water.
Some germs can survive without oxygen, yet most living things cannot live without it.
Oxygen is needed for fire to burn and is used in making explosives and jet fuel. Welders use it to fuel their welding torches.
Two chemists, Carl Scheele and Joseph Priestley discovered oxygen independently of each other, in the 1700s. Scheele called it "fire air" and Priestley called it "dephlogisticated air". French chemist Antoine Lavoisier named it oxygen in 1777.