Oxygen is a non-flammable gas that is colorless and odorless. It has a melting point of 54.36 Kelvin and a boiling point of 90.19 Kelvin. Oxygen speeds the rate of combustion by acting as an oxidizing agent.
Oxygen has the atomic number of 8 on the periodic table because it has eight protons in its nucleus. Its most abundant form has eight neutrons, with less abundant forms having nine or 10. Oxygen has two allotropes, or chemical forms. The most common is oxygen gas, which consists of two oxygen atoms bonded together. The second is ozone, which consists of three oxygen atoms bonded together.