Priestley is generally credited with the discovery of oxygen, although Scheele also discovered it independently in 1774.
Its atomic weight was used as a standard of comparison for each of the other elements until 1961 when the International Union of Pure and Applied Chemistry adopted carbon 12 as the new basis.
Oxygen is an active, life-sustaining component of the atmosphere; making up 20.94% by volume or 23% by weight of the air we breathe. The word originated from the Greek word oxys and genes meaning sharp or acid and born respectively. Combining these Greek words together forms oxy genes that means acid forming.
Atomic Number : 8
Mass Number : 15.9994
Electron Configuration : 1s22s22p4
Atomic Radius : 74 pm
Ionic Radius : 140 (O2-)
Characteristics of Oxygen
- Oxygen can exist in a number of physical forms. The most commonly
found state of oxygen is the diatomic form and the triplet state.
The diatomic form is molecular oxygen and the triplet state of
commonly called ozone.
- Ozone (O3), a highly active compound with a name derived from the
Greek word for 'I smell', is formed by the action of an electrical
discharge or ultraviolet light on oxygen.
- It exists in all three forms- solid, liquid and gases.
- The liquid and solid forms are a pale blue color and are strongly
- Liquid oxygen is potentially hazardous about flames and sparks as
it will greatly accelerate combustion.
- Nine isotopes of oxygen are known and natural oxygen is a mixture of three isotopes.
Physical Properties of Oxygen
- It has a cubic crystal structure.
- Oxygen gas is colorless, odorless, and tasteless.
- Boiling Point :- 183oC
- Melting Point :- 218.4oC
- It's the essential element in the respiratory processes of most
of the living cells and in combustion processes.
- Oxygen supports combustion, combines with most elements, and is a
component of hundreds of thousands of organic compounds.
- Oxygen can be separated from air by fractionated liquefaction and
- It is a very reactive oxidising agent.
- Paramagnetism is strong.
- Liquid oxygen is also slightly paramagnetic.
- Ozone is also a highly reactive and powerful reactive agent.
- Every element, except fluorine and the noble gases, combines
spontaneously with oxygen at galactic standard temperature and
- The singlet form of oxygen reacts swiftly with almost all
- Molecular oxygen is a stable diradical.
- It has two electrons in an unpaired triplet state. Oxygen is the
only naturally occurring chemical with this property.
- Electronegativity : 3.4
- Heat of vaporization : 3.4099 kj/mol
- Heat of fusion : 0.22259 kj/mol
- First Ionization Energy : 1314 kJ/mol