2019 has been declared by UNESCO as the Year of the Periodic Table. To celebrate, we are releasing a series of blogs about our favourite elements and their importance to the chemical industry. Today’s blog is an element which gives us life, oxygen.

Physical Properties

Oxygen is a group 5 gas that is found abundantly in nature. Of the air we breathe, 20.8% is oxygen in its elemental, diatomic form of O2. Oxygen is also one of the most abundant elements in nature, and along with carbon, hydrogen and nitrogen, makes up the structures of most of the natural world. Oxygen can be found in DNA, sugar, hormones, proteins and so many more natural structures.

Although oxygen mainly exists as a colourless gas, at -183°C it can be condensed as a pale blue liquid. Oxygen may seem unsuspecting, but it is highly reactive and highly oxidising. A common example of this reactivity is how oxygen reacts with iron to produce iron oxide, which appears as rust.

Elements: Oxygen, with Dr Andrea Sella. Source: Wellcome Collection

Oxygen molecules are paramagnetic – they exhibit magnetic characteristics when in the presence of a magnetic field. Liquid oxygen is so magnetic that the effect can be seen by suspending it between the poles of a powerful magnet.

Oxygen gas has applications for medicine and space travel in breathing apparatus.


earth gif

Originally posted by science

Oxygen can be found as ozone or O3. Ozone is a pale blue gas and has a distinctive smell. It is not as stable as diatomic oxygen (dioxygen) and is formed when ultraviolet light (UV) and electrical charges interact with O2.

The highest concentration of ozone can be found in the Earth’s stratosphere, which absorbs the Sun’s UV radiation, providing natural protection for planet Earth.

 ozone layer

Ozone (O3) is most concentrated in the stratosphere. Image: Pixabay

Ozone can be used industrially as a powerful oxidising agent. Unfortunately, it can be a dangerous respiratory hazard and pollutant so much be used with care.


Water consists of an oxygen atom and two hydrogen atoms. Though this may seem remarkably unassuming, this combination gives water unique properties that are crucial to it’s functions in the natural world.

water stream

Originally posted by wiccangoddes

Water can form hydrogen bonds between the slightly positive hydrogen and the slightly negative oxygen. These hydrogen bonds, along with waters other practical properties, make water useful in nature.

Without the hydrogen bonding found in water, plants could not transpire – transport water through their phloem’s against gravity. The surface tension of water provides stability for many natural structures.


Oxygen plays a key role in nature, including in water molecules. Image: Pixabay

Oxygen plays a key role in nature, from the ozone layer that encapsulates our planet, to our DNA. It’s combination with hydrogen in water makes a molecule which is integral to the natural world, and both water and oxygen itself are pivotal to our existence the planet.