Oxygen is primarily considered an element. In its most common form, it exists as a diatomic molecule (O2), which consists of two oxygen atoms bonded together. An element is a pure substance that cannot be broken down into simpler substances by chemical means, and oxygen is listed on the periodic table as a distinct element with the atomic number 8.
To break it down further:
- Atom: The smallest unit of matter that retains the properties of an element. Oxygen atoms (O) can exist individually.
- Molecule: A group of two or more atoms bonded together. The diatomic form O2 is the most common representation of oxygen in the atmosphere.
- Element: A substance made of only one type of atom. Oxygen, as an element, is defined by its atomic number and properties.
In summary, oxygen can refer to an atom when discussing individual oxygen atoms, it can refer to a molecule when talking about O2, but as a whole, it is classified as an element in the context of chemistry.