3 Trends in lattice enthalpies

Trends in Lattice Enthalpies The strength of a enthalpy of lattice formation depends on the following factors 1. The sizes of the ions: The larger the ions, the less negative the enthalpies of lattice formation (i.e. a weaker lattice). As the ions are larger the charges become further apart and so have a weaker attractive force between them. 2. The charges on the ion: The bigger the charge of the ion, the greater the attraction between the ions so the stronger the lattice enthalpy (more negative values). The lattice enthalpies become less negative down any group. e.g. LiCl, NaCl, KCl, RbCl e.g group 1 halides (eg NaF KI) have lattice enthalpies of around – 700 to -1000 group 2 halides (eg MgCl2 ) have lattice enthalpies of around –2000 to –3500 group 2 oxides eg MgO have lattice enthalpies of around –3000 to – 4500 kJmol-1