Structures of Materials

Structures of Materials

1. Simple molecular substances

   • Low melting and boiling points
     • Above 20 degrees= solid Below 20 degrees= gas
   • Cannot conduct electricity
   • Non-metals
   • Because the molecules are small, the intermolecular forces are weak.
   • Can be both elements and compounds
   • Only a few atoms held together by strong covalent bonds.

2. Giant Covalent

   • Bonds are formed by electron pairs shared between atoms. The positively charged nuclei of both atoms are attracted to the negatively charged shared electrons. This is a covalent bond.
   • High melting points
   • Atoms are usually arranged into giant regular lattices.
   • Variable conductivity
   • Diamond
     • A form of carbon in which each carbon atom is joined to four other carbon atoms.
     • Very hard
     • High melting point
     • Non-conductor of electricity
   • Graphite
     • Form of carbon in which the carbon atoms form layers. These layers can slide over each other.
     • Much softer than diamond
     • Conducts electricity

3. Giant Ionic

   • Have a crystal lattice structure. This is a regular pattern of rows and columns.
     • Giant ionic lattice- the regular 3D pattern is repeated over and over again in all directions.
   • Made up of positively and negatively charged ions.
     • Ionic bonds are the electrostatic forces of attraction between oppositely charged ions.
   • High melting and boiling points
     • A lot of energy is required to overcome the attractive forces.
   • Conducts electricity in the liquid state or when dissolved in water.