Oxygen is colorless, odorless, gas element denoted by the atomic symbol, O. Its atomic number is 8 and it has an atomic weight of 15.9994. It has a melting point of -360° F (-218° C) and a boiling point of -183 ° F (-297° C).

The discovery of oxygen marked a milestone in the history of science. Until the Renaissance, most European scientists believed in the ancient Greek notion that air was an element, one of four basic substances from which all other things are made. Then, during the 1600s and 1700s, chemists began to identify the different gases contained in air and to clarify the connection between air, combustion, and life.

In the 1770s Swedish chemist Carl Wilhelm Scheele prepared oxygen by heating several different compounds. Scheele called the gas fire air because he found that many substances require it in order to burn. Around the...