Exam 1 Under: Flash Cards Crystal 3-D Periodic array of atoms. Crystallinity Long range order and periodicity of atoms. Ideal Crystal An infinite regular repetition in space of identical structural untis Basis / Motif Group of atoms, ions, or molecules associated with each lattice point. Lattice A regular periodic arrangement of points in space. Crystal Structure Basis plus Lattice Unit Cell A small repetitive volume that forms the complete lattice Lattice Constants Dimensions of the unit cell Lattice Parameter Dimensions of the unit cell and the associated angles between the axes Lattice Coefficients Lattice constants expressed in unit cell dimensions Primitive Cell Parallelpiped defined by primitive axes Equivalent Site Lattice sites with fully identical surroundings Coordination Number Number of nearest neighbors Amorphous Material Material lacking long-range order, glassy Polymorphism A material that can exist in more than one crystalline form Allotropy Another name for Polymorphism Crystal system scheme by which crystals are classified according to unit cell geometry Miller Indicies Set of three integers that designate crystallographic planes Atomic Packing Factor The fraction of space filled by atoms within a particular crystal structure Related posts: Chapter 1 chapter 1 Chapter 12 Elements General Elements memory cards Elements of the Periodic Table.