Why is oxygen always stated as O2?

Answer 1

Because oxygen in its natural state is a molecule of two oxygen atoms. Hence O2.

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Oxygen is a diatomic molecule, which means it's always found in nature as O2. Oxygen (and the other diatomic molecules) are never one atom because they are so reactive, they always bond with something else, therefore oxygen is O2. Other diatomic molecules are: Hydrogen (H2), Nitrogen (N2), and the halogens (Fluorine, Chlorine, Bromine, and Iodine)

Answer 2

Oxygen is very reactive. It has 6 valence electrons - electrons in its outermost energy level. Of these 6 two of them are non paired meaning that they are available to form a chemical bond. Oxygen has a tendency to gain two electrons when bonding to form a stable electron configuration.

If nothing else is available then oxygen shares two of its electrons with another oxygen atom that also shares two electrons forming a stable diatomic molecule O2: O=O.

Oxygen is making do with sharing electrons to fill its orbitals.

Oxygen is still reactive and will swap some other element for its oxygen partner if possible. For example burning fuel:

C8H16 + 12O2 --> 8CO2 + 8H2O

Oxygen is now bonded either with carbon: 2x2 electrons to share: O=C=O

or with two atoms hydrogen: each with 1 electyron to share: H-O-H.

Answer 3

Ozone is comprised of three oxygen atoms. The oxygen we breathe is written as O2.

Answer 4

Because oxygen is a gas with a diatomic molecule.