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The cycle is concerned with the formation of an ionic compound from the reaction of a metal (often a Group I or Group II element) with a halogen or other non-metallic element such as oxygen. Born–Haber cycles are used primarily as a means of calculating lattice energy (or more precisely enthalpy [note 1]), which cannot otherwise be measured ...
For many substances, the formation reaction may be considered as the sum of a number of simpler reactions, either real or fictitious. The enthalpy of reaction can then be analyzed by applying Hess' law, which states that the sum of the enthalpy changes for a number of individual reaction steps equals the enthalpy change of the overall reaction.
A representation of Hess's law (where H represents enthalpy) Hess's law of constant heat summation, also known simply as Hess's law, is a relationship in physical chemistry and thermodynamics [1] named after Germain Hess, a Swiss-born Russian chemist and physician who published it in 1840.
In these cases the polarization energy E pol associated with ions on polar lattice sites may be included in the Born–Haber cycle. As an example, one may consider the case of iron-pyrite FeS 2 . It has been shown that neglect of polarization led to a 15% difference between theory and experiment in the case of FeS 2 , whereas including it ...
For example, Na–Cl and Mg–O interactions have a few percent covalency, while Si–O bonds are usually ~50% ionic and ~50% covalent. Pauling estimated that an electronegativity difference of 1.7 (on the Pauling scale) corresponds to 50% ionic character, so that a difference greater than 1.7 corresponds to a bond which is predominantly ionic ...
The Born–Haber cycle, an approach to analyze reaction energies, is developed by German scientists Max Born and Fritz Haber. Sydney Chapman and David Enskog systematically develop a kinetic theory of gases. Jan Czochralski invents a method for growing single crystals of metals.
In some reactions between highly reactive metals (usually from Group 1 or Group 2) and highly electronegative halogen gases, or water, the atoms can be ionized by electron transfer, [16] a process thermodynamically understood using the Born–Haber cycle. [17] Salts are formed by salt-forming reactions. A base and an acid, e.g., NH 3 + HCl → ...
A chance meeting with Fritz Haber in Berlin in 1918 led to discussion of how an ionic compound is formed when a metal reacts with a halogen, which is today known as the Born–Haber cycle. In World War I he was originally placed as a radio operator, but his specialist knowledge led to his being moved to research duties on sound ranging.