Is Oxygen a Compound or an Element?

A common question that I’ve seen online is whether oxygen is an element or a compound. So which is it? Is oxygen a compound or an element?

Oxygen is an element. It is a substance consisting of only a single type of atom. “O” is its official chemical symbol, and 8 is its atomic number. This means that an oxygen atom features 8 protons in its nucleus.

Read on to learn more about oxygen, as well as the difference between a chemical compound and a chemical element.

Is Oxygen a Compound or an Element?

is oxygen a compound

Oxygen (O) is a chemical element. Oxygen is a diatomic molecule, meaning it consists of two O atoms bonded together chemically. “O” is its official chemical symbol, while 8 is its atomic number. This means that an oxygen atom contains 8 protons and 8 electrons in its nucleus.

I recommend that you know the difference between a chemical compound and a chemical element since this will help you remember at all times that oxygen is an element and not a compound.

What Is a Chemical Element?

A chemical element (or element) refers to any substance that can never be decomposed into simpler substances using ordinary chemical processes.

Chemical elements are essential in such a way that all matter is composed of elements.

General Observations

There are currently over a hundred chemical elements. Approximately 20% of these elements do not exist in nature or are only visible in trace amounts. There are also those that scientists prepared in the laboratory.

Among all the known chemical elements, 11 are gases under ordinary conditions. Examples include oxygen, chlorine, fluorine, nitrogen, and hydrogen.

Two chemical elements are liquids, namely mercury and bromine.

However, two more elements melt at approximately or a little above room temperature. These are gallium and cesium. Then, the rest of the elements are solids.

Chemical elements can combine to create an ample variety of substances we know as chemical compounds. Our scientists have probably created more than a million compounds, and they keep on discovering more and more of these every day.

When two or more elements combine, a compound forms.

Upon combining, the elements lose their separate identities while the compound produced has characteristics that are exceedingly different from its constituent elements.

For example, 2 moles of water form when Hydrogen (2 moles H2) and Oxygen (1 mole O2) combine. Water has different properties than hydrogen and oxygen.

So is oxygen gas a compound? Is oxygen an element? Yes, oxygen is an element. The oxygen atom contains 8 protons and 8 electrons in its nucleus.

What Is a Chemical Compound?

Britannica defines a chemical compound as “any substance composed of identical molecules consisting of atoms of two or more chemical elements.” Meaning, a chemical compound forms when two or more chemical elements combine chemically.

General Observations

All the matter on Earth has atoms of over a hundred different chemical elements and chemical compounds.

In the case of a pure element, this consists of atoms characteristic only of that element. Examples of these are hydrogen, carbon, or oxygen, among many others. These elements are unique from each other.

As earlier mentioned, chemical elements may combine to form chemical compounds. These compounds form their own uniqueness. In fact, their characteristics may be extremely different from the characteristics of their constituent elements.

Let’s go back to our previous example-water. As we have mentioned, 2 moles of water form when Hydrogen (2 moles H2) and Oxygen (1 mole O2) combine. Water has unique properties to hydrogen and oxygen.

Molecular and Ionic Chemical Compounds

There are two types of chemical compounds, namely, molecular and ionic. The compounds methane and water are examples of molecular compounds. Molecular compounds form when two or more nonmetal elements chemically combine.

When metal and non-metal elements combine, ionic compounds form. An example of an ionic chemical compound is sodium chloride, which has a chemical symbol of NaCl.

is oxygen an element

The formula for sodium chloride is NaCl. It consists of an equal number of sodium ions (Na+) and chloride ions (Cl-). The sodium ions, however, have a charge of a positive one. At the same time, the chloride ions have a charge of a negative one.

So, if you are confused and have been asking yourself, is oxygen a compound? The answer is no, and it is not. It is a chemical element that can help us form chemical compounds.

Organic and Inorganic Chemical Compounds

Chemical compounds exhibit an inexplicable array of characteristics. At ordinary pressures and temperatures, they can exist as solids, liquids, or gases.

Compounds create colors that resemble those of the rainbow. Some compounds are essential to life. At the same time, some compounds are toxic to humans.

A compound can change in odor, color, or even toxicity by merely changing a single atom. And this explains why there are over a million compounds present, and there are still more being discovered.

Aside from molecular and ionic compounds, there are also organic and inorganic compounds.

Organic Compounds

Organic compounds are called such as they were originally isolated from living organisms. Suffice it to say that they consist of rings or chains of carbon atoms.

Carbon has a variety of ways to bond not only with itself but with other elements. Hence, the presence of over nine million organic compounds to date.

Inorganic Compounds

Evidently, those compounds that are not considered organic are categorized as inorganic compounds.

If you are asking, is oxygen an organic molecule, it is not in the same manner that it is not an inorganic molecule. This is because it is simply an atom by itself.

Again, is Oxygen a compound or an element? Pure elemental oxygen occurs as O2, a diatomic molecule (oxygen bonded to another oxygen). But scientists still characterized it as an element since it only contains one type of element (O).

More About Oxygen

By now, you should know the answer to the question, is oxygen gas a compound?

Pure oxygen gas is definitely not a chemical compound. Instead, it is a chemical element. It is a substance that consists of only a single type of atom. “O” is its official chemical symbol, whereas 8 is its atomic number. This means that an oxygen atom features 8 protons in its nucleus.

This chemical element is a gas at room temperature and features no color, taste, or smell. If two oxygen atoms are strongly joined together with a covalent double bond, they produce dioxygen, a chemical symbol of O2.

Ozone (O₃)

The ozone forms in the Earth’s stratosphere and is considered another form of pure oxygen. Ozone is formed when O2 molecules separate into single oxygen atoms using ultraviolet (UV) light.

The single oxygen atoms then latch onto the O2 molecules to produce the ozone. The chemical formula of which is O3.

There is more UV present in the stratosphere. Thus, the production of higher concentrations of O3. The UV is filtered out by the ozone layer and minimizes the chance to split O2 molecules in the troposphere. The troposphere is the lower atmosphere or exactly where we live.

However, the ozone can still be produced in the troposphere when O2 is placed under extreme pressure and heat. Engines of vehicles have the ideal conditions to form ozone, which is, in fact, a toxin.

That’s why modern vehicles make use of catalytic converters. This allows O3 to convert back to O2.

Solid and Liquid Oxygen

Oxygen interestingly becomes a liquid when it is cooled to -183 degrees Celsius. Liquid oxygen is mainly produced to become a propellant for rockets, such as the Rocket Lab’s Electron rocket.

It is also interesting to know that solid oxygen is formed when oxygen is placed at a temperature below -218.79° Celsius. Another interesting fact is that whether the oxygen is in its solid or liquid state, the substances produce a light sky blue color.

The Occurrence of Oxygen

It is common knowledge that oxygen is everywhere.

is oxygen gas a compound

Here are some interesting facts are oxygen and its importance to us:

  1. By mass, oxygen is the most abundant chemical element in the human body as our bodies are composed of 70% water.
  2. The Earth’s oceans are made up of oxygen by mass. While hydrogen atoms in water are more, hydrogen also has less mass. Water, by mass, contains approximately 90% oxygen.
  3. In the atmosphere, oxygen is considered the second most abundant gas. Approximately 21% of air is oxygen. But oxygen is highly reactive as it is capable of easily combining with other chemical elements. Interestingly, oxygen is replenished by plants and all other photosynthetic organisms.
  4. When it comes to the Earth’s crust, oxygen is the most abundant element by mass. Oxygen produces chemical compounds with silicon and many other atoms to create minerals. These include sand and quartz.
  5. After helium and hydrogen, oxygen is the third highly abundant chemical element in the entire universe.

Oxygen and Life

Oxygen is indeed essential to life. Most living things use oxygen for cellular respiration. Cellular respiration is the process in which energy is obtained by cells.

For instance, as part of the air, living things such as land animals and humans breathe oxygen. Oxygen is absorbed into our blood and then carried to the cells of our body.

In the case of fishes, they use gills to get dissolved oxygen from the water. Insects breathe oxygen too. Using their spiracles, oxygen passes into a network of tubes known as the trachea. The spiracles are small external openings that insects have.

Plants undergo the cellular respiration process too. Similarly, plants need oxygen too. In a different process called photosynthesis, plants take in carbon dioxide and let out oxygen.

The photosynthesis rate varies, and it all depends on how exposed the plants are to light. If there is low light, the photosynthesis rate is lower than the cellular respiration rate.

But if there is a bright light, the photosynthesis rate is higher than the respiration rate. In the case of the latter, more oxygen is produced. Whatever excess oxygen is produced will automatically be released into the atmosphere.


Oxygen, by itself, will never be capable of producing fire. Nonetheless, it is important for combustion. In fact, oxygen is one of the three components that make up the fire triangle. The two other components are heat and fuel.

The heat generated by the fire sustains the fire. For as long as there are sufficient fuel and oxygen, you can never put off the fire.

This explains why there are two types of fire extinguishers. One is the water-based fire extinguishers that remove the heat to put off the fire. The other one is the carbon dioxide and dry chemical extinguishers that cut off the supply of oxygen to put off the fire.

Conclusion – Is Oxygen an Element or a Compound?

If you are curious, is oxygen a compound or an element? The answer is that oxygen is a chemical element. It is definitely not a chemical compound. It is a substance featuring only a single type of atom.

Its official chemical symbol is “O,” while its atomic number is “8.” This means that an oxygen atom contains 8 protons in its nucleus.

Oxygen is one of the most interesting chemical elements. It is highly essential to our lives as it forms part of the air we breathe. But this element can also be toxic when mixed with other elements to form toxic chemical compounds.