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)