Atomic spacing
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 bonds which bind atoms together. [1]
The spacing between atoms in most ordered solids is on the order of a few angstroms (a few tenths of a nanometer). In very low density gasses (for example, in outer space) the average distance between atoms can be as large as a meter.
The atomic spacing is usually determined by passing an electromagnetic wave of known frequency through the material, and using the laws of diffraction to determine its atomic spacing.