Entablature being called petrification. The structure of the entablature varies with the three classical orders: Doric, Ionic, and Corinthian. In each, the proportions of the subdivisions (architrave, frieze, cornice) are defined by the proportions of the column in the order. In Roman and Renaissance interpretations, it is usually approximately a quarter of the height of the column. Variants of entablature that do not fit these models are usually derived from them. Pure classical Doric entablature is simple. The architrave, the lowest band, is split, from bottom to top, into the guttae, the regulae, and the taenia. The frieze is dominated by
Ionic radius Ionic radius Ionic radius, "r", is the radius of an atom's ion in ionic crystals structure. Although neither atoms nor ions have sharp boundaries, they are sometimes treated as if they were hard spheres with radii such that the sum of ionic radii of the cation and anion gives the distance between the ions in a crystal lattice. Ionic radii are typically given in units of either picometers (pm) or angstroms (Å), with 1 Å = 100 pm. Typical values range from 30 pm (0.3 Å) to over 200 pm (2 Å). The concept can be extended to solvated ions