Britannica Sources used in this answer

How does a homonuclear diatomic molecule differ from a heteronuclear diatomic molecule?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

representations of molecular structure — molecule Several methods of representing a molecule's structure. In Lewis structures, element symbols represent atoms, and dots represent electrons surrounding them. A pair of shared electrons (covalent bond) may also be shown as a single dash. The ball-and-stick model better illustrates the spatial arrangement of the atoms. For aromatic compounds, the Kekulé structure is common, in which each bond is represented by a dash, carbon atoms are implied where two or more lines meet, and hydrogen atoms are usually omitted. Bond-line formulas, similar to the Kekulé structure, are often used for complex nonaromatic organic compounds. Sugars are often drawn as Fischer projections, in which the carbon “backbone” is drawn as a straight vertical line, with carbon atoms implied where horizontal lines intersect the vertical one.

The primary difference between homonuclear and heteronuclear diatomic molecules lies in the identity of the atoms that compose them.

Homonuclear diatomic molecules consist of two atoms of the same element, such as oxygen ( $O_{2}$ ) or hydrogen ( $H_{2}$ ). Because the atoms are identical, the distribution of electrical charge is uniform, resulting in a nonpolar bond with a dipole moment of zero.12
Heteronuclear diatomic molecules consist of two atoms of different elements, such as sodium chloride ( $N a C l$ ). Because these atoms have different electronegativities, the shared electrons are drawn more strongly toward one atom than the other. This creates an unequal distribution of charge, leading to partial charges on the atoms and the formation of an electric dipole.12

While both types of molecules are bonded in a straight line, the nature of their bonding—ranging from covalent to ionic—exists on a continuum determined by the electronegativity difference between the bonded atoms.12