Sources of Oxygen

Oxygen is the most abundant of all elements in the crust of the earth. It is present in sand and rocks in the form of silicon dioxide, and in most of the common compounds like oxides, carbonates, nitrates, etc. It is also present in air, water and land as organic compounds like carbohydrates, proteins, etc.

Earth's curst contains nearly 49% of oxygen by mass. In sand and rocks, it can be as high at 53% by mass. Water contains 89% oxygen by mass, air 23% by mass and 20.9% by volume.

Some basic features of Oxygen

Symbol	O
Molecular formula	O2
Atomic number	8
Mass number	16
Atomic mass	16
Molecular mass	32
Electronic configuration	2,6
Valency	-2
Isotopes	16 17 18 O O O 8 8 8