Answer is: two oxygen atoms.
Molecule of oxygen is nonpolar because double linear bond.
Oxygen (O) is an element with atomic number 8, it means it has eight protons and eight electrons, so atom has neutral charge. Oxygen is a nonmetal.
Two valence electrons from both oxygen atoms form double bond at oxygen molecule.
Together, nitrogen (N₂) and oxygen (O₂) by volume account for 99,03% of the gases composing the dry air in the lower atmosphere.