According to the National Center for Biotechnology Information, the chemical formula for oxygen is O2. The O stands for the oxygen molecule, while the 2 represents the need for two oxygen molecules to form the element.
O2 is also known as molecular oxygen, dioxygen, hyperoxia and pure oxygen. NCBI states that oxygen is "the most abundant element on earth and essential for respiration." Oxygen has the atomic symbol O, the atomic number 8 on the periodic table and an atomic weight of 15.99903; 15.99977. The two-dimensional structure of oxygen is represented by "o=o," which shows the two oxygen molecules connected to form an element.