Oxygen: The Most Versatile Element

The Element Oxygen

Introduction to Oxygen

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Oxygen is one of the most common elements on earth and in the universe. It has a wide range of properties including paramagnetism and combustibility. Oxygen is a colorless, odorless gas, and is the third most abundant element both on earth and in the broader universe. It has many applications such as in medicine and fuel combustion. Due to its highly reactive nature, oxygen unsurprisingly plays a vital role in both nature and industry. Most importantly, oxygen is responsible for so many vital biological processes, life on earth would not exist without its abundance.

Ten Interesting and Fun Facts about Oxygen

  1. All aerobic living organisms need oxygen to survive and thrive. This includes plants, animals, and fungi. Only anaerobic organisms can survive without oxygen.
  2. Oxygen used to be the atomic weight standard before it was replaced with carbon-12 in 1961.
  3. During the carboniferous period 350 million years ago, oxygen levels in the atmosphere were 35%. This allowed insects to grow to be near 10x their modern size!
  4. Natural oxygen has three isotopes, but oxygen-16 is most abundant, responsible for approximately 99.7% of the element  as it is found in nature.
  5. When oxygen’s outer electrons jump to an excited state, they produce bright colors such as purple and green. This is how oxygen creates the aurora borealis!
  6. Solid oxygen is very difficult to produce because it has such a low melting point.
  7. Singular oxygen atoms are very rare in nature–they are in fact, diatomic! Oxygen atoms are almost always bonded to another oxygen atom, or to some other element.
  8. Oxygen can form in the core of stars
  9. Freshwater contains more oxygen per liter than seawater. Seawater only contains about 82% as much oxygen as freshwater.
  10. Oxygen is the most abundant element in the human body by mass. Nearly ⅔ of our body weight is oxygen!

 Oxygen in the Periodic Table

Oxygen is the 8th element on the periodic table and has the symbol O. It has an atomic number of 8 because it has 8 protons. It is a Chalcogen, meaning it belongs to group 16 of the periodic table. A single oxygen atom has 6 valence electrons and has a charge of -2. Oxygen is one of the most electronegative elements, with a 3.44 on the Pauling scale, and is therefore located on the upper right-hand side of the periodic table. It is located in the p-block and gas a configuration of [He] 2s²2p⁴

Oxygen in the Environment

Oxygen is most commonly found as an allotrope, specifically O2 and O3 (ozone). Ozone is much more reactive than O2 and plays an important role in atmospheric chemistry by absorbing UV radiation from sunlight. Without the Ozone Layer of the earth’s atmosphere, the UV index at the surface would be far too high for living organisms to thrive. As greenhouse gases destroy the ozone over time, more UV radiation enters the earth’s atmosphere and causes the globe to warm.

Oxygen’s Importance to Life:

Oxygen is famously known for being a requirement for cellular respiration. It releases energy within the mitochondria to produce adenosine triphosphate during oxidative phosphorylation, often represented by the chemical equation:

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Diatomic oxygen diffuses through membranes in the lungs and into red blood cells and binds to hemoglobin, giving blood its distinctive red color. The average human inhales approximately 2 grams of oxygen per minute at rest.

Free oxygen gas was extremely rare on earth prior to the existence of the first single-celled organisms. Photosynthetic bacteria and archaea evolved 3.5 billion years ago and began to increase the concentration of oxygen in the atmosphere. However, it took over a billion years for aerobic organisms to become the dominant form of life on earth and start to drastically increase the volume of oxygen in the atmosphere. For the last 500 million years, atmospheric oxygen levels have fluctuated between 15-30%, and sit at around 21% today. 

Element Oxygen’s Applications in Today’s World

Rocket Fuel

Oxygen is a primary reactant in the exothermic combustion reactions used in industries across the world. One of the most famous uses for liquid oxygen in particular, dubbed “LOX,” is its role as an oxidizer in the production of rocket fuel, first utilized by NASA scientist Robert Goddard in 1962. It is still the primary combustor in rocket fuel today. 


Gaseous oxygen is frequently used in medicine, specifically for patients struggling to breathe independently. Oxygen tanks with tubes connecting to the nose are administered to hospital patients in order to assist with breathing and keep blood oxygen levels stable. Normally, people breathe in air, which is combusted of 79% Nitrogen and 21% Oxygen. The nitrogen is breathed in and then out again without being changed. In medicine, the oxygen is so pure to avoid contamination, that the patients are only breathing in the gas that they need.


Diatomic oxygen readily combines with metals to produce oxides and is also responsible for corrosion. Corrosion creates a protective coating around a metal, which gives oxygen to numerous industrial applications. It famously reacts with Iron to form Iron(III) Oxide, which leads to rust via oxidation. Oxygen oxidizes fuels when something is burning. Starting a fire would be very difficult if there was less oxygen in the atmosphere. 


Pure oxygen is typically obtained through electrolysis, a process in which an electric current is run through water. This gives the water molecules enough energy to break the bonds between hydrogen and oxygen, releasing pure gas of oxygen and hydrogen. In a laboratory setting, materials can be combusted more efficiently if the oxygen concentration of the atmosphere is increased. Oxygen oxidizes fuels when something is burning. Starting a fire would be very difficult if there was less oxygen in the atmosphere!

Oxygen is also one of the elements that can partake in hydrogen bonding, along with nitrogen and fluorine. This bonding capability allows it to form strong compounds with higher boiling points, such as water.

When and How was Oxygen Discovered

History of Oxygen

Air was first identified as an “element” by the ancient Greeks more than 2500 years ago. They categorized air with fire, wind, and water.

However, the proper discovery of oxygen is mainly credited to English scientist Joseph Priestly. Priestly performed various experiments on samples of air and was able to prove that it was not a uniform compound, but a mixture of many different elements, each of which reacted differently.

There are some who credit German chemist Carl Wilhelm Steele with the discovery of oxygen in 1773, although this is sometimes disputed. Steele did not publish his experimental results until 1774, just after Priestley published his. It may be that both scientists discovered the element at the same time independently, similar to how Isaac Newton and Gottfried Wilhelm Leibniz both discovered the foundations of calculus.

Where is Oxygen Found in the Universe?

In its elemental form, oxygen is the 3rd most common element in the earth’s crust and the 2nd most common element in the earth’s atmosphere. Diatomic oxygen and ozone are rarely found outside of these two circumstances. Compounds of oxygen, however, are very common in nature and in industry.

Isolation of Oxygen

Oxygen is isolated via a method known as the Fractional Distillation Method. This is performed by containing atmospheric air, cooling it to -181˚ Celsius, at which point the oxygen is liquified. This liquid oxygen is then harvested. It can either be maintained in its liquid form with low temperatures, or it can easily be converted into a gas.

Oxygen Chemistry – Compounds, Reactions, Oxidation States

Chemical Properties of Oxygen

Oxygen is highly reactive and most common forms oxides with other elements, but it is capable of forming a wide variety of compounds. Oxygen serves as a potent oxidizing agent and is the 2nd most electronegative element, behind fluorine. At standard temperature and pressure, (STP) oxygen forms diatomic molecules in a colorless, odorless gas. Oxygen is also soluble in water, but this is a temperature-dependent property.

Liquid Oxygen

Liquid oxygen has a much more noticeable blue color than gaseous oxygen, and is comparatively a much stronger oxidizing agent, and is also more reactive. Oxygen in its liquid form tends to create highly energetic reactions in the presence of organic molecules, often in the form of combustion or detonation reactions. It is strongly paramagnetic as a result of the parallel spin of unpaired electrons. Its paramagnetism is so strong that two poles of a magnet. can actually suspend liquid oxygen Unpaired electrons within molecular orbitals are responsible for a slightly bluish color that is easier to spot when oxygen is in its liquid form. 

Oxygen Oxidation States

Oxygen can exhibit multiple oxidation states, but most commonly exhibits -2. The -1 oxidation state is present in peroxides and persulfates. Oxidation states +1, +2 are very rare for oxygen, and occur when combined with fluorine.

Oxygen Compounds

Oxygen is a highly reactive element. The noble gases helium and neon are the only elements oxygen does not form compounds with, and that is because they are incredibly stable on their own.

  • H2O – water
  • ​​Fe2O3 – Iron(III) Oxide (rust)
  • CO2 – Carbon Dioxide (product of respiration)
  • SiO2 – Silicon dioxide(found in granite and sand)
  • Al2O – aluminum oxide (in bauxite and corundum)
  • CaCO3. – calcium carbonate (in limestone and silicates)
  • C2H4O – Ethylene oxide (used to make antifreeze)

Oxygen is also present within many organic functional groups, including alcohols, esters, and ketones. It is one of the two primary atoms in a carbonyl, a fundamental building block for organic molecules.

Physical Properties of Oxygen:

In its gaseous form, oxygen is colorless, odorless, and tasteless.

  • Oxygen Symbol: O
  • Melting point: 54 K
  • Boiling point: 90 K
  • Oxidation states: -2 (most common), -1, +1, +2 (less common)
  • Density: 1.43 g/L
  • Atomic weight: 15.99 u
  • Atomic number: 8
  • Electronegativity: 3.44
  • Classification: Nonmetal, Chalcogen
  • Natural abundance: 46.6% of Earth’s crust
  • Electron shell configuration:  [He] 2s²2p⁴
  • Ionization energy: 13.61 eV

Where can I buy Oxygen?

Oxygen canisters can be purchased over-the-counter at most pharmacies. This can be used for medical uses but also athletic performance. A mountain climber may need to use cans of oxygen to maintain cardiovascular health when approaching a certain altitude. Liquid oxygen, though, must be purchased directly from a lab or chemical company because it must be kept at incredibly low temperatures to maintain this lower energy state.