O₂ refers to molecular oxygen, which is an allotrope of oxygen consisting of two oxygen atoms bonded together. It is one of the products formed in the given equation.
Related terms
Allotrope: Different forms or variations of an element that exist in the same physical state but have different properties.
Product: A substance formed as a result of a chemical reaction.
Catalyst: A substance that speeds up the rate of a chemical reaction without being consumed itself.