- Polar covalent bonds occur when electrons are shared unequally between atoms, resulting in a partial positive charge on one atom and a partial negative charge on the other. This occurs when the atoms involved have different electronegativities, which is the ability of an atom to attract electrons.

- In the case of oxygen, the two oxygen atoms share electrons equally, resulting in a nonpolar covalent bond. This is because oxygen has an electronegativity of 3.44, which is the same as itself. This means that the electrons are shared equally between the two atoms and there is no partial positive or negative charge on either atom.