Atomic spacing refers to the distance between the
nuclei of
atoms in a material. This space is extremely large compared to the
size of the
atomic nucleus, and is related to the
chemical bond
A chemical bond is a lasting attraction between atoms or ions that enables the formation of molecules and crystals. The bond may result from the electrostatic force between oppositely charged ions as in ionic bonds, or through the sharing o ...
s which bind atoms together. In solid materials, the atomic spacing is described by the
bond lengths of its atoms. In ordered solids, the atomic spacing between two bonded atoms is generally around a few
ångström
The angstromEntry "angstrom" in the Oxford online dictionary. Retrieved on 2019-03-02 from https://en.oxforddictionaries.com/definition/angstrom.Entry "angstrom" in the Merriam-Webster online dictionary. Retrieved on 2019-03-02 from https://www.m ...
s (Å), which is on the order of 10
−10 meters. However, in very low density gases (for example, in
outer space) the average distance between atoms can be as large as a
meter. In this case, the atomic spacing isn't referring to bond length.
The atomic spacing of crystalline structures is usually determined by passing an
electromagnetic wave of known
frequency through the material, and using the laws of
diffraction
Diffraction is defined as the interference or bending of waves around the corners of an obstacle or through an aperture into the region of geometrical shadow of the obstacle/aperture. The diffracting object or aperture effectively becomes a s ...
to determine its atomic spacing. The atomic spacing of
amorphous materials
In condensed matter physics and materials science, an amorphous solid (or non-crystalline solid, glassy solid) is a solid that lacks the long-range order that is characteristic of a crystal.
Etymology
The term comes from the Greek ''a'' ("wi ...
(such as
glass) varies substantially between different pairs of atoms, therefore diffraction cannot be used to accurately determine atomic spacing. In this case, the average bond length is a common way of expressing the distance between its atoms.
Example
Bond length can be determined between different elements in molecules by using the
atomic radii
The atomic radius of a chemical element is a measure of the size of its atom, usually the mean or typical distance from the center of the nucleus to the outermost isolated electron. Since the boundary is not a well-defined physical entity, there ...
of the atoms.
Carbon bonds with itself to form two covalent network solids.
Diamond's C-C bond has a distance of Sqrt
/4 ≈ 0.154 nm away from each carbon since a
diamond ≈ 0.357 nm, while
graphite's C-C bond has a distance of a/Sqrt
≈ 0.142 nm away from each carbon since a
graphite ≈ 0.246 nm. Although both bonds are between the same pair of elements they can have different bond lengths.
References
Nuclear physics
{{Nuclear-stub