Oxygen

Oxygen is a non-metallic element of atomic number 8. Its symbol is O, the atomic weight is 15.9994, the specific gravity is 1.10535 (compared to air), the melting point is -361°F (-218.4°C), and the boiling point is -297.4°F (-183°C).

Oxygen is a non-metal in group 16 of the periodic table. Its three stable isotopes have atomic weights of 16, 17, and 18. The first is by far the most abundant, constituting 99.763% of all oxygen atoms occurring in nature. Oxygen-17 makes up an additional 0.037%, and oxygen-18, 0.200% of all oxygen atoms. A number of radioactive isotopes of the element have also been prepared, the most widely used commercially being oxygen-15, which decays by the emission of a positron with a half life of 122 seconds.

Oxygen was discovered independently by the Swedish chemist Carl Scheele and the English chemist Joseph Priestley in the period 1773-1774. The element was given its name by the French chemist Antoine Laurent Lavoisier in 1779. Its name comes from the French word for "acid-former," reflecting Lavoisier's incorrect belief that all acids contain oxygen.