Oxygen was discovered by Joseph Priestley in 1744. Carl W. Scheele of Sweden found the presence of the element two years before, but failed to publish it. Scheele found a gas that enhances combustion while heating several compounds, including mercury oxide, manganese oxide and potassium nitrate. Scheele called the gas 'fire air'. Priestley, on the other hand heated mercury oxide with the help of a 12-inch burning lens. Surprisingly, he observed a gas that made a candle burn more brightly. Priestley called the gas 'dephlogisticated air'. However, the name oxygen was given to the element by Antoine Lavoisier who also carried out experiments similar to that of Priestley and found that oxygen accounts for 20% of air.
||Gas at 298 K
|CAS Registry ID
|Group in periodic table
|Period in periodic table
|Block in periodic table
||Colorless as a gas, liquid is pale blue
||54.36 K (-218.79°C or -361.82°F)
||90.20 K (-182.95°C or -297.31°F)
|Phase at room temperature
Oxygen is one of the most abundant elements on Earth. Oxygen accounts for 20.9% of the atmosphere, 45% of the Earth’s crust (as oxide minerals) and also accounts for almost all of the mass of water on Earth (89%). It is found in a huge number of natural minerals including sulfates, phosphates, carbonates and oxides. Furthermore, it is the third most abundant element in the universe following hydrogen and helium.
Oxygen has totally 13 isotopes with mass numbers from 12O to 24O. 16O, 17O and 18O are the naturally-occurring isotopes with respective natural abundances of 99.8%, 0.04% and 0.2%.
The following are common methods used to produce oxygen:
- It can be prepared by decomposition of potassium chlorate or hydrogen peroxide using manganese dioxide catalyst.
- Electrolysis of acidified water using Hofmann voltammeter also yields oxygen at the positive electrode.
- It can also be obtained through decomposition of salts, oxides and water.
- Heating mercury within a confined volume of air yields mercuric oxide which can be decomposed to produce pure oxygen.
Biological components including DNA within the human body constitutes oxygen and hence oxygen is essential for all organisms. Every human requires oxygen for breathing. However, over-exposure to oxygen may lead to lung damage.
The key properties of oxygen are listed below:
- It is a colorless, odorless and tasteless gas
- It readily dissolves in cold water
- It is highly reactive and form oxides with almost all elements except noble gases
- Liquid oxygen is strongly paramagnetic
- It exists in three allotropic forms- monoatomic, diatomic and triatomic
- It supports combustion.
Some of the major applications of oxygen include the following:
- It is used in oxy-acetylene torch for cutting and welding metals
- It is used to remove carbon impurities from the steel during steel production
- A mixture of liquid oxygen and powdered charcoal is used as an explosive
- It is used as an oxidant for rocket fuel
- It is used in large quantities for the synthesis of ethylene oxide, methanol and ammonia.
- Dissolved oxygen is essential for the life of fish.