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THE SOLID STATE, , 1. Calculation of numer of particles / atoms / ions in a Unit Cell :, , , , , , 2. Type of Numer of Relationship, Unit Cell Particles per between edge, Unit Cell length (a) and, radius (0) of, ‘Simple cubic, 4, Body centred cubic 2 a= Br, Face centred cubic 4 azar, Density of unit cell (d), ZxM, e axn,, , Where Z is rank of unit cell (no. of atoms per unit cell), m is molar mass!, atomic mass, ‘a’ is edge length of the cube, ‘a is volume of cubic unit, cell and Ny is Avogatro number., , 4. Packing efficiency = Pe cS ar x 100, Here 'M’ is molar mass 'r’ is radius of atom, ‘d’ is density and N, is, Avogaotro's number (6.022 x 10° mot")., Rank of unit cell can be computed by packing efficiency value, , Type of Packing Rank of, Unit Cell efficiency Unit Cell, , sc 52.4% 1, , Bcc 68.% 2, , Foc 74% 4