![]() ![]() However, for less symmetrical and more polar lattices such as those with C n, C nh, and C nv symmetries, significant changes in the electron density can occur, causing deviations from spherical shape these deviations make ionic radii more difficult to measure. For instance, lattices with O h and T d symmetries are considered to have high symmetry thus the electron densities of the component ions occupy relatively-spherical regions and ionic radii can be measured fairly accurately. The point group symmetry of a lattice determines whether or not the ionic radii in that lattice can be accurately measured (Johnson 1973). For a given ion, the ionic radius increases with increasing coordination number and is larger in a high-spin state than in a low-spin state.Īccording to group theory, the idea of ionic radii as a measurement of spherical shapes only applies to ions that form highly-symmetric crystal lattices like Na + and Cl. Ionic radius is not a permanent trait of an ion, but changes depending on coordination number, spin state, and other variables (Shannon 1976). After comparing many compounds, chemist Linus Pauling assign a radius of 140 pm to O 2- and use this as a reference point to determine the sizes of other Ionic Radii (Jensen 2010). However, it is to consistently and accurately determine the proportions of the ionic bonds. ![]() The ionic radius of an atom is measured by calculating its spatial proportions in an ionic bond with another ion within a crystal lattice. Measurement and Factors Affecting Ionic Radii
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