Source: Data from CRC Handbook of Chemistry and Physics (2004).īecause the lattice energy depends on the product of the charges of the ions, a salt having a metal cation with a +2 charge (M 2 +) and a nonmetal anion with a −2 charge (X 2−) will have a lattice energy four times greater than one with M + and X −, assuming the ions are of comparable size (and have similar internuclear distances). Energies of this magnitude can be decisive in determining the chemistry of the elements. Representative values for calculated lattice energies, which range from about 600 to 10,000 kJ/mol, are listed in Table 4.2.1. The value of the constant k′ depends on the specific arrangement of ions in the solid lattice and their valence electron configurations, topics that will be discussed in more detail in the second semester.
We see from Equation 4.4 that lattice energy is directly related to the product of the ion charges and inversely related to the internuclear distance. As before, Q 1 and Q 2 are the charges on the ions and r 0 is the internuclear distance. U, which is always a positive number, represents the amount of energy required to dissociate 1 mol of an ionic solid into the gaseous ions.
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