Oxygen
Definition and meaning of Oxygen in chemistry.
![Oxygen element card: symbol O, atomic number 8, atomic mass 15.999, electron configuration [He] 2s² 2p⁴, oxidation states -2, Nonmetal, group 16, period 2, gas at room temperature.](/assets/images/terms/oxygen-chemical-element.webp)
Oxygen is a highly reactive nonmetal element with the symbol O and atomic number 8. It acts as a powerful oxidizing agent that forms strong chemical bonds with most other elements. This element is the most abundant on Earth, making up about 46% of the solid crust by mass.
In more detail
At room temperature and standard pressure, two oxygen atoms bond together to make dioxygen gas. This colorless, odorless gas has the formula O2 and makes up 20.9% of our atmosphere by volume. Plants and algae continuously remake this gas through photosynthesis, which converts solar energy into chemical energy.
In living things, oxygen is crucial for cellular respiration, the process that extracts energy from food. During respiration, oxygen helps cells break down glucose sugar to release the energy stored in its chemical bonds. Inside cells, it acts as the final electron acceptor in the electron transport chain to generate ATP.
Many students incorrectly assume that oxygen is highly flammable and burns on its own. In reality, oxygen only supports the burning of other fuels and does not catch fire itself. For industrial use, companies obtain pure oxygen by cooling air until it liquefies and separating the parts.
They also use special mineral filters called zeolites to trap nitrogen gas and let pure oxygen pass through. This purified gas is useful for making steel, welding metals, and helping patients in hospital beds.
Key facts
| Field | General Chemistry |
|---|---|
| Symbol | O |
| Atomic number | 8 |
| Atomic mass | 15.999 u |
| Category | Nonmetal |
| Formula | O2 |
| State at STP | Gas |
During a typical combustion reaction, oxygen gas reacts very quickly with a flammable fuel source like methane gas. Combustion is simply the scientific term for burning a substance in the presence of an oxidizer. This energetic chemical reaction releases large amounts of heat, water vapor, and carbon dioxide gas into the air. If you limit the amount of oxygen, the reaction becomes incomplete and produces toxic carbon monoxide instead.
Frequently asked questions
Why is oxygen necessary for human survival?
Oxygen is required for cellular respiration, which is a metabolic process that extracts energy from nutrients. This process produces ATP to power all our cellular functions.
Is oxygen flammable?
Oxygen itself is not flammable and will not catch fire alone. However, it is an oxidizer that vigorously supports and accelerates the burning of other materials.
What is the difference between oxygen and ozone?
Oxygen gas contains two oxygen atoms bonded together, while ozone contains three oxygen atoms bonded together. Ozone forms a protective layer in the upper atmosphere but is toxic to breathe near the ground.
Related terms
Sources & references
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