Is oxygen gas (O2) a compound or an element?

Neither, it's a molecule. An element is a single unique atom. A molecule is two or more atoms bonded together that may or may not be the same element. A compound is two or more different atoms that are bonded. read more

Oxygen is an element. A compound is two or more elements chemically combined. A mixture is two or more elements physically combined (ie. just mixed together). Oxygen gas is made of molecules containing only oxygen. Normal atmospheric oxygen is O2 and ozone is O3. So, it certainly isn't a compound. read more

Oxygen is a pure substance. The element oxygen is found in the air most commonly as oxygen gas. Oxygen is one of the seven diatomic elements: H2 N2 O2 F2 Cl2 Br2 and I 2 eye2 not to be confused with the # 12 and it is not known if At ( the element Astatine ) is diatomic. read more

Oxygen readily forms compounds with one or more elements because its chemical reactivity allows its atoms to form molecules with one or more other kinds of atoms. Oxygen is also the name of a pure bulk substance in which oxygen atoms pair up to form O2 molecules, a gas at room temperature. read more