Oxygen is a chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group on the periodic table, which also includes sulfur, selenium, and tellurium.
Oxygen is a highly reactive element and is able to exist in multiple forms, or allotropes. The two most common allotropes of oxygen are:
Molecular oxygen (O2): This is the most familiar form of oxygen and makes up the majority of the air we breathe. Molecular oxygen is a colorless, odorless gas that is essential for life.
Ozone (O3): Ozone is a highly reactive form of oxygen that is found in the stratosphere. It is a pale blue gas that absorbs ultraviolet radiation from the sun and helps to protect the earth from harmful effects.
In addition to these two allotropes, there are several other forms of oxygen that are less common and found under specific conditions, such as in extreme temperatures or pressures. These include singlet oxygen, triplet oxygen, and superoxide.