Introduction to Structures and Types of Solids
- Crystalline solids: have highly regular arrangement of their components (NaCl)
- Amorphous solids: have considerable disorder in their structures (glass)
- Lattice: represents the positions of the components in a crystalline solid
○ Unit Cell: the smallest repeating unit of the lattice
Types of Crystalline Solids
- Classify solids according to what type of component occupies the lattice points
Atomic Solids (have atoms at lattice points)
| Metallic Solids | Network Solids | Group 18/8A | Molecular Solids | Ionic | |
| Components at Lattice point | Metal atoms | Nonmetalatoms | Noble gas atoms | Whole, covalently bonded molecules Nonmetal + Nonmetal (ones that aren’t NS) | Ions |
| Bonding & Forces | Delocalized electrons | Covalent bonding that leads to large molecules | LDF forces | LDF and possibly D-D attraction | Ionic bonds No interMFs |
| Properties | Conductor Wide range of hardness and MP | Typically brittle Poor Conductors Very high MP and BPHard | Very low MP | Low MPPoor Conductors / Good Insulators Soft & weaker than NSolids bcus of weaker dispersion forces | Hard/brittle (easy to break) High MP (bcuz e- locked in lattice)Poor Conductor/ Good Insulator (e- trapped) |
| Example | FeCu | Carbon, Silicon dioxide | NeAr | S2I2 | NaCl |
Network Solids
- Network solids:
○ Examples to know: C (diamond), C (graphite), most silicon and boron compounds
Carbon-a Special Network Solid
- 3 allotropes of Carbon: Are all network solids but differences are due to the way they are connected
- Coal: amorphous
- Diamond: hardest natural substance on earth bcuz network is very strong as a result of covalent bonding between atoms
○ Insulator bcuz diamond has electrons that are locked into lattice with little space to move
- Graphite: slippery (sheets formed can slide past each other; the pi bonds extend above and below plane
○ Not as strong as diamond bcuz is held together by weaker dispersion forces
○ The delocalization of pi bonds accounts for the electrical conductivity of graphite bcuz network not as tightly bound (electrons can move around)