What is Oxygen?

Oxygen is the third most abundant element in the universe and makes up nearly 21% of the earth's atmosphere.

It is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal. Oxygen lies in group 16 and thus has a valency of -2.

Oxygen is required by all living organisms to respire and is, therefore, a very important element.