Crystals essays

Crystals essays What is a crystal? A crystal is a solid substance with definite geometric shapes and molecules that are arranged in a repeating pattern (Compton ¹s ). Crystals have fixed angles between its faces, which have distinct edges. If the faces of a crystal can reflect light, then it will sparkle (Stangle). Crystals have constant angles because of the regular arrangement of its particles. There are seven types of crystals: cubic, tetragonal, orthorhombic, hexagonal, trigonal, monoclinic, and triclinic (Dr. Boyle). Crystals are classified by the shapes of their lattice or the  ³regular, periodic configuration of particles ² (American Heritage). There are two different types of lattices. There are primitive lattices where there is only one lattice point per unit cell. There are also non-primitive lattices. They are the ones with more than one lattice point per unit cell. Crystals can also be classified by their physical/chemical properties. There are four types of crystals classified this way. They are covalent, metallic, ionic, and molecular (Dr. Boyle). A covalent crystal is a crystal which is one big molecule. They usually have extremely high melting points. An example of a covalent crystal is a diamond and zinc sulfide (Dr.Boyle). Metallic crystals have high melting points and densities. They are metal atoms which sit on lattice sites while the outer electrons from these atoms flow freely around the lattice (Dr. Boyle). Ionic crystals are crystals where the individual atoms do not have covalent bonds among themselves. These atoms are held together by electrostatic forces. They are also very hard and have a relatively high melting point. Sodium chloride (NaCl, salt) is an example of an ionic crystal (Dr. Boyle). Molecular crystals are crystals where there are  ³recognizable molecules in the structure and the crystal is held together by non-covalnet interactions ² such as hydrogen bonding (Dr. Boyle). Sugar i...