bond length

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A graph with energy on the vertical axis and internuclear separation on the horizontal axis, showing a red curve dipping into a well; the well's depth represents bond strength and its position indicates bond length.

bond length

physics

Also known as: average bond length

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June 22, 2026

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A graph with energy on the vertical axis and internuclear separation on the horizontal axis, showing a red curve dipping into a well; the well's depth represents bond strength and its position indicates bond length. — molecular potential energy Figure 10: A molecular potential energy curve. The strength of the bond is indicated by the depth of the well below the energy of the separated atoms (to the right), and the bond length is the corresponding internuclear separation.

The term "bond length" in physics refers to the average distance between the nuclei of two bonded atoms in a molecule. This distance is determined by the balance between the attractive forces holding the atoms together and the repulsive forces pushing them apart.1

In chemistry, bonds between atoms can be classified as sigma bonds or pi bonds. A pi bond involves electrons occupying orbitals roughly parallel to the line between two atoms, and it exists alongside a sigma bond. Carbon atoms are unique in their ability to form extensive networks of covalent bonds with themselves and other elements, forming the basis of organic compounds. The specific arrangement and type of bonds (single, double, or triple) influence the bond length and the overall structure and properties of the molecule.231

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spectroscopy
Energy states of real diatomic molecules
…molecule undergoes vibrational motion, the bond length will oscillate about an average internuclear separation. If the oscillation is harmonic, this average value will not change as the vibrational state of the molecule changes; however, for real molecules the oscillations are anharmonic. The potential for the oscillation of a molecule is…
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…molecule undergoes vibrational motion, the bond length will oscillate about an average internuclear separation. If the oscillation is harmonic, this average value will not change as the vibrational state of the molecule changes; however, for real molecules the oscillations are anharmonic. The potential for the oscillation of a molecule is…
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chemical bonding
The quantum mechanics of bonding
…the vibrational properties of the bond) equal to the bond dissociation energy and hence indicates the tightness with which the two atoms are held together. The steepness of the walls of the curve, which shows how rapidly the energy changes as the nuclear separation changes, indicates the rigidity of the…
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…the vibrational properties of the bond) equal to the bond dissociation energy and hence indicates the tightness with which the two atoms are held together. The steepness of the walls of the curve, which shows how rapidly the energy changes as the nuclear separation changes, indicates the rigidity of the…
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chemical compound
Infrared (IR) spectroscopy
…distance known as the average bond length. These movements are termed stretching vibrations. In addition, the bond axis (defined as the line directly joining two bonded atoms) of one bond may rock back and forth within the plane it shares with another bond or bend back and forth outside that…
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…distance known as the average bond length. These movements are termed stretching vibrations. In addition, the bond axis (defined as the line directly joining two bonded atoms) of one bond may rock back and forth within the plane it shares with another bond or bend back and forth outside that…
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water
Liquid water
The O―H distance (bond length) is 95.7 picometres (9.57 × 10⁻¹¹ metres, or 3.77 × 10⁻⁹ inches). Because an oxygen atom has a greater electronegativity than a hydrogen atom, the O―H bonds in the water molecule are polar, with the oxygen bearing a partial negative charge (δ−) and…
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The O―H distance (bond length) is 95.7 picometres (9.57 × 10⁻¹¹ metres, or 3.77 × 10⁻⁹ inches). Because an oxygen atom has a greater electronegativity than a hydrogen atom, the O―H bonds in the water molecule are polar, with the oxygen bearing a partial negative charge (δ−) and…
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