Oxygen is a chemical element with symbol O and atomic number 8. It is a member of the chalcogen group on the periodic table and is a highly reactive nonmetal and oxidizing agent that readily forms compounds (notably oxides) with most elements. By mass, oxygen is the third-most abundant element in the universe, after hydrogen and helium.
Three reasons Oxygen stands out
- 1
Essential for respiration and combustion.
- 2
It is the most abundant element in the Earth's crust by mass.
- 3
In liquid form it is a pale blue colour and is strongly attracted to magnets.
The reactive partner behind respiration
Oxygen’s appetite for electrons makes combustion possible and lets cells release energy from food. Photosynthetic organisms continually replenish atmospheric oxygen, but the element also dominates Earth’s crust by mass inside silicate minerals and oxides. Its pale-blue liquid form is visibly drawn toward a strong magnet.