British scientist Joseph Priestley (pictured) liberated oxygen gas, corroborating the discovery of the element by the German-Swedish chemist Carl Wilhelm Scheele.

Joseph Priestley was an English chemist, Unitarian, natural philosopher, separatist theologian, grammarian, multi-subject educator and classical liberal political theorist. He published over 150 works, and conducted experiments in several areas of science.

Oxygen is a chemical element; it has symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and a potent oxidizing agent that readily forms oxides with most elements as well as with other compounds. Oxygen is the most abundant element in Earth's crust, making up almost half of the Earth's crust in the form of various oxides such as water, carbon dioxide, iron oxides and silicates. It is the third-most abundant element in the universe after hydrogen and helium.

Carl Wilhelm Scheele was a German-Swedish pharmaceutical chemist.