CHM 11500 Lecture Notes - Lecture 24: Single Crystal, Repeat Unit, Close-Packing Of Equal Spheres

• School: Purdue University
• Department: Chemistry
• Course: CHM 11500
• Professor: Ramachandran- Claridge

Document Summary

Crystalline solids have a repeating pattern of molecules/atoms. When most liquids are cooled, they eventually freeze and form crystalline solids. Solids in which the atoms, ions, or molecules are arranged in a definite repeating pattern. Single crystals: one large ordered domain (diamonds, sugar grains, salt grains) Polycrystalline solids: multiple smaller ordered domains (chunks of ice, metals, granite) Amorphous: don"t have a high ordered structure (glass, wax) Large single crystals are stable but hard to form. Atoms/molecules form ordered arrays to maximize bonding/intermolecular interactions. Polycrystalline materials form when several small crystals start growing in the same solution. Single crystal silicon used for circuits and solar cells. Computer chips and many solar cells take advantage of the superior electronic properties of single crystals. Make sure the crystallization starts in just one place. Amorphous solids result when molecules in the liquid can"t move easily (often when they"re very large) As the temperature is lowered: molecules stop in random positions.