Editing Ionic bonding (section)

==Strength of the bonding==
{{Main|Lattice energy}}

For a solid crystalline ionic compound the [[enthalpy]] change in forming the solid from gaseous ions is termed the [[lattice energy]]. The experimental value for the [[lattice energy]] can  be determined using the [[Born–Haber cycle]]. It can also be calculated (predicted) using the [[Born–Landé equation]] as the sum of the [[electrostatic potential energy]], calculated by summing interactions between cations and anions, and a short-range repulsive potential energy term. The [[electrostatic potential]] can be expressed in terms of the interionic separation and a constant ([[Madelung constant]]) that takes account of the geometry of the crystal. The further away from the nucleus the weaker the shield. The [[Born–Landé equation]] gives a reasonable fit to the lattice energy of, e.g., sodium chloride, where the calculated (predicted) value is −756&nbsp;kJ/mol, which compares to −787&nbsp;kJ/mol using the [[Born–Haber cycle]].<ref>David Arthur Johnson, ''Metals and Chemical Change'', Open University, Royal Society of Chemistry, 2002, {{ISBN|0-85404-665-8}}</ref><ref>Linus Pauling, ''The Nature of the Chemical Bond and the Structure of Molecules and Crystals: An Introduction to Modern Structural Chemistry'', Cornell University Press, 1960 {{ISBN|0-801-40333-2}}  {{doi|10.1021/ja01355a027}}</ref> In aqueous solution the binding strength can be described by the [[Bjerrum plot|Bjerrum]] or Fuoss equation as function of the ion charges, rather independent of the nature of the ions such as polarizability or size.<ref>Schneider, H.-J.; Yatsimirsky, A. (2000) ''Principles and Methods in Supramolecular Chemistry''. Wiley {{ISBN|9780471972532}}</ref> The strength of salt bridges is most often evaluated by measurements of equilibria between molecules containing cationic and anionic sites, most often in solution.<ref>{{cite journal | vauthors = Biedermann F, Schneider HJ | title = Experimental Binding Energies in Supramolecular Complexes | journal = Chemical Reviews | volume = 116 | issue = 9 | pages = 5216–300 | date = May 2016 | pmid = 27136957 | doi = 10.1021/acs.chemrev.5b00583 }}</ref> Equilibrium constants in water indicate additive free energy contributions for each salt bridge. Another method for the identification of hydrogen bonds in complicated molecules is [[crystallography]], sometimes also NMR-spectroscopy.

The attractive forces defining the strength of ionic bonding can be modeled by [[Coulomb's law|Coulomb's Law]]. Ionic bond strengths are typically (cited ranges vary) between 170 and 1500 kJ/mol.<ref>Soboyejo, W.O (2003). Mechanical properties of engineered materials. Marcel Dekker. pp. 16–17. {{ISBN|0-203-91039-7}}. {{OCLC|54091550}}.</ref><ref>Askeland, Donald R. (January 2015). The science and engineering of materials. Wright, Wendelin J. (Seventh ed.). Boston, MA. pp. 38. {{ISBN|978-1-305-07676-1}}. {{OCLC|903959750}}.</ref>