Editing Salt (chemistry) (section)

== History of discovery ==
[[Image:X-ray spectrometer, 1912. (9660569929).jpg|thumb|X-ray spectrometer developed by W. H. Bragg]]

In 1913 the structure of [[sodium chloride]] was determined by [[William Henry Bragg]] and his son [[William Lawrence Bragg]].<ref>{{cite journal|last1=Bragg|first1=W. H.|last2=Bragg|first2=W. L.|title=The Reflection of X-rays by Crystals|journal=Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences|date=1 July 1913|volume=88|issue=605|pages=428–438|doi=10.1098/rspa.1913.0040|bibcode=1913RSPSA..88..428B|s2cid=13112732 }}</ref><ref>{{cite journal|last1=Bragg|first1=W. H.|title=The Reflection of X-rays by Crystals. (II.)|journal=Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences|date=22 September 1913|volume=89|issue=610|pages=246–248|doi=10.1098/rspa.1913.0082|bibcode=1913RSPSA..89..246B|doi-access=free}}</ref><ref name=sherman/> This revealed that there were six equidistant [[Coordination number|nearest-neighbours]] for each atom, demonstrating that the constituents were not arranged in molecules or finite aggregates, but instead as a network with long-range [[Crystal structure|crystalline]] order.<ref name=sherman/> Many other [[inorganic compound]]s were also found to have similar structural features.<ref name=sherman/> These compounds were soon described as being constituted of ions rather than neutral [[atom]]s, but proof of this hypothesis was not found until the mid-1920s, when [[X-ray reflectivity|X-ray reflection]] experiments (which detect the density of electrons), were performed.<ref name=sherman>{{cite journal|last1=Sherman|first1=Jack|title=Crystal Energies of Ionic Compounds and Thermochemical Applications|journal=Chemical Reviews|date=August 1932|volume=11|issue=1|pages=93–170|doi=10.1021/cr60038a002}}</ref><ref>{{cite journal|last1=James|first1=R. W.|last2=Brindley|first2=G. W.|title=A Quantitative Study of the Reflexion of X-Rays by Sylvine|journal=Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences|date=1 November 1928|volume=121|issue=787|pages=155–171|doi=10.1098/rspa.1928.0188|bibcode=1928RSPSA.121..155J|doi-access=free}}</ref>

Principal contributors to the development of a [[theoretical]] treatment of ionic crystal structures were [[Max Born]], [[Fritz Haber]], [[Alfred Landé]], [[Erwin Madelung]], [[Paul Peter Ewald]], and [[Kazimierz Fajans]].{{sfn|Pauling|1960|p = 505}} Born predicted crystal energies based on the assumption of ionic constituents, which showed good correspondence to [[thermochemistry|thermochemical]] measurements, further supporting the assumption.<ref name=sherman/>