CHEM 122 1st Edition Lecture 9Outline of Last LectureI. Packinga. Hexagonalb. CcpII. Coordination Numbers of Cubic Unit CellsIII. Sodium Chloride Structure typeIV. CsCl Structure type Outline of Current Lecture I. Types of Crystalline solidsa. Ionic solidsb. Molecular solidsc. Covalent-Network solidsi. Diamond structureii. Graphite structured. Metallic solidsCurrent LectureTypes of Crystalline Solids- Ionic Solids: Consists of ions held together by ionic bondingo Strength of electrostatic attraction increases with ionic charge along with meltingpoint.o Structure of ionic solids depends on the size of ions and their chargeso Properties of Ionic solids:These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best Used as a supplement to your own notes, not as a substitute. Relatively hard High melting points Brittle/breakable Doesn’t conduct electricity as solids (molten state does)- Molecular Solids: atoms or molecules held together by intermolecular forces.o Soft with low melting points due to weak attractive forces- Covalent-Network Solids: atoms held together by strong covalent bonds in a large network.o Much harder with higher melting points than molecular solids; stronger forces of attraction between atoms. o Consist of nonmetals or metalloids only.o COVENANT NETWORKS NEEDED TO KNOW FOR TEST: Diamond and graphite (both C) Quartz (SiO2) Silicon carbide (SiC) Solid boron (B) Boron nitride (BN) Solid silicon (Si)o Diamond Structure: extended array of C atoms bonded together with a single covalent bond. Tetrahedral geometry (3-D) Very hard; very high melting point (3550 C)o Graphite structure: Consists of 2-D array of carbon atoms Hexagonal rings (sheets) slide past one another easily giving it a slippery feel.o Diamond and graphite are allotropes (different forms of the same element.)- Metallic Solids: metal atoms that are packed together so that they are touching Metallic Bonding: the bonding of metal atoms Malleability and ductility: valence electrons of metal atoms are spread out over entire solid to give the metals their ability to conduct
View Full Document
Unlocking...