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In chemistry, a formula unit is the smallest unit of a non-molecular substance, such as an ionic compound, covalent network solid, or metal. [1] [2] It can also refer to the chemical formula for that unit. Those structures do not consist of discrete molecules, and so for them, the term formula unit is used.
Born–Haber cycles are used primarily as a means of calculating lattice energy (or more precisely enthalpy [note 1]), which cannot otherwise be measured directly. The lattice enthalpy is the enthalpy change involved in the formation of an ionic compound from gaseous ions (an exothermic process ), or sometimes defined as the energy to break the ...
The Born–Landé equation is a means of calculating the lattice energy of a crystalline ionic compound. In 1918 [1] Max Born and Alfred Landé proposed that the lattice energy could be derived from the electrostatic potential of the ionic lattice and a repulsive potential energy term. [2]
The resulting compound is called an ionic compound, and is said to be held together by ionic bonding. In ionic compounds there arise characteristic distances between ion neighbours from which the spatial extension and the ionic radius of individual ions may be derived. The most common type of ionic bonding is seen in compounds of metals and ...
The ionic strength of a solution is a measure of the concentration of ions in that solution. Ionic compounds , when dissolved in water, dissociate into ions. The total electrolyte concentration in solution will affect important properties such as the dissociation constant or the solubility of different salts .
Kapustinskii replaced r 0, the measured distance between ions, with the sum of the corresponding ionic radii. In addition, the Born exponent, n, was assumed to have a mean value of 9. Finally, Kapustinskii noted that the Madelung constant, M, was approximately 0.88 times the number of ions in the empirical formula. [2]
The Born–Mayer equation is an equation that is used to calculate the lattice energy of a crystalline ionic compound.It is a refinement of the Born–Landé equation by using an improved repulsion term.
For example, the compound dichlorine hexoxide has an empirical formula ClO 3, and molecular formula Cl 2 O 6, but in liquid or solid forms, this compound is more correctly shown by an ionic condensed formula [ClO 2] + [ClO 4] −, which illustrates that this compound consists of [ClO 2] + ions and [ClO 4] − ions. In such cases, the condensed ...