{{short description|Distance between two nucleus}} [[File:Diamond_and_graphite_comparison.png|thumb|(Top) Diamond [[crystal structure]], depicting an atomic spacing of 0.154 nm. (Bottom) Graphite crystal structure, depicting an atomic spacing of 0.142 nm.]] '''Atomic spacing''' refers to the distance between the [[atomic nucleus|nuclei]] of [[atom]]s in a material. This space is extremely large compared to the [[nuclear size|size]] of the [[atomic nucleus]], and is related to the [[chemical bond]]s which bind atoms together.<ref>{{Cite book | edition = 8th | publisher = Wiley | isbn = 047141526X | last = Kittel | first = Charles | title = [[Introduction to Solid State Physics]] | date = 2004-11-11 }}</ref> In solid materials, the atomic spacing is described by the [[bond length]]s of its atoms. In ordered solids, the atomic spacing between two bonded atoms is generally around a few [[ångström]]s (Å), which is on the order of 10<sup>−10</sup> meters (see [[Lattice constant]]). However, in very low density gases (for example, in [[outer space#Environment|outer space]]) the average distance between atoms can be as large as a [[meter]]. In this case, the atomic spacing is not 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 [[Bragg diffraction|diffraction]] to determine its atomic spacing. The atomic spacing of [[amorphous solid|amorphous materials]] (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.{{cn|date=September 2023}}
==Example== [[Bond length]] can be determined between different elements in molecules by using the [[atomic radius|atomic radii]] of the atoms. [[Carbon]] bonds with itself to form two covalent network solids.<ref>{{cite web |last1=Rossi |first1=Miriam |title=How can graphite and diamond be so different if they are both composed of pure carbon? |url=https://www.scientificamerican.com/article/how-can-graphite-and-diam/ |website=Scientific American |publisher=Scientific American |accessdate=October 9, 2007}}</ref> [[Diamond]]'s C-C bond has a distance of <math>\frac{\sqrt{3}a}{4} \approx 0.154\ \text{nm}</math> away from each carbon since <math>a_{\text{diamond}} \approx 0.357\ \text{nm}</math>, while [[graphite]]'s C-C bond has a distance of <math>\frac{a}{\sqrt{3}} \approx 0.142\ \text{nm}</math> away from each carbon since <math>a_{\text{graphite}} \approx 0.246\ \text{nm}</math>. Although both bonds are between the same pair of elements they can have different bond lengths.<ref>{{cite book |author=Brown |author2=Lemay |author3=Bursten |title=Chemistry the Central Science |date=1997 |publisher=Simon and Schuster |location=Upper Saddle River, NJ |pages=412–413}}</ref>
==References== {{Reflist}}
[[Category:Nuclear physics]]
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