Oxygen element | Properties, Abundance, Uses and History

Characteristics of oxygen

Oxygen is the element from the periodic table of symbol O, and atomic number 8. This means that in its nucleus there are 8 protons (apart from neutrons), and 8 electrons orbiting them. Oxygen is a very reactive non-metal. In addition, it is the element that makes life on Earth possible.

At room temperature, oxygen is found in the form of a colourless, tasteless, and odourless gas. It is a poor conductor of electricity and heat, and it is denser than air. Below a temperature of -183ºC, oxygen is found in the liquid state, and below -218ºC it converts into a solid. Both in its liquid and solid state, oxygen appears in a pale blue colour.

Due to its high reactivity, on the Earth oxygen is found in many compounds. One of the most common is water, being also present (in minute quantities) in the form of carbon dioxide. Moreover, oxygen compounds are very abundant on the Earth’s mantle, including a great variety of silicates.


Oxygen is the third most abundant element in the universe.

In the Earth’s atmosphere, this element is the second most abundant, representing 21% of the latter. In addition, ozone (formed by three oxygen molecules), and present in the upper layers of the atmosphere, offers protection to terrestrial life against the harmful UV rays emitted by the sun.

Oxygen is constantly replenished in the atmosphere by the photosynthesis process. Approximately 45-70% of the Earth’s oxygen is produced by green algae and cyanobacteria in the ocean, whereas the rest is produced by land plants.

Uses of oxygen

  • Oxygen is mainly used in the manufacturing, refinement and melting of steel and other metals.
  • This element is used in the purification processes of various metals.
  • It is also widely used as an oxidant for rocket fuel, by combining hydrogen and liquid oxygen.
  • The manufacturing of various chemicals also requires the usage of oxygen.
  • Oxygen is an element used in the manufacturing of life support kits.


In 1771, the English chemist Carl W. Scheele discovered oxygen by heating diverse compounds, including manganese oxide, mercury oxide and potassium nitrate. He observed that the produced gas intensified the combustion process, and he named it “fire air”.

Independently, and not knowing the results of Scheele (which he didn’t publish until 1777), the chemist Joseph Priestly also discovered oxygen, in 1774, by heating mercury oxide. The mercury emitted a gas that made a candle burn faster. Priestly also discovered that the obtained gas could support life.

The word oxygen comes from the Greek words “oxys” and “genes”, and they mean “acid forming”. This name was proposed by Antoine Lavoisier, who observed the tendency for this element to form acid substances.

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