Nitrogen dioxide (NO2) is a covalent molecule. This means that the atoms in NO2 are held together by sharing electrons, rather than by ionic bonds. In an ionic bond, one atom transfers electrons to another atom, creating a positive and negative ion. In a covalent bond, the atoms share electrons, creating a stable molecule.

In NO2, the nitrogen atom shares three electrons with each of the two oxygen atoms. This creates a double bond between the nitrogen and each oxygen atom. The double bonds are what hold the NO2 molecule together.