Homonuclear
Definition and meaning of Homonuclear in chemistry.
Homonuclear describes a molecule, ion, or bond formed between atoms of the same chemical element. The term is most often applied to homonuclear diatomic molecules, such as O2 or N2, in which two identical atoms are joined by a covalent bond.
In more detail
Because both atoms in a homonuclear bond have identical electronegativity, the bonding electron pair is shared perfectly equally. This makes the bond purely nonpolar covalent and gives the molecule a zero net dipole moment, since there is no charge asymmetry to create one. Seven elements exist as homonuclear diatomic molecules under standard conditions: hydrogen, nitrogen, oxygen, fluorine, chlorine, bromine, and iodine. The term contrasts with heteronuclear, which describes bonds or molecules formed between atoms of different elements, such as carbon monoxide (CO) or hydrogen chloride (HCl).
Key facts
| Field | General Chemistry |
|---|---|
| Homonuclear diatomic elements | H2, N2, O2, F2, Cl2, Br2, I2 |
| Bond polarity | Nonpolar covalent (zero electronegativity difference) |
| Opposite term | Heteronuclear |
Oxygen gas (O2) is a homonuclear diatomic molecule: both atoms are oxygen, the O-O bond is nonpolar, and the molecule has no permanent dipole moment.
Frequently asked questions
Are homonuclear diatomic molecules polar?
No. Since both atoms are the same element, they have identical electronegativity, so the shared electrons are distributed symmetrically and the molecule has no net dipole moment.
What is the difference between homonuclear and heteronuclear molecules?
A homonuclear molecule contains only one element, like N2, while a heteronuclear molecule contains two or more different elements, like CO or HF.