Lvl 2 Chem: Types of Substances

Lvl 2 Chem: Types of Substances

1. Metallic

   • Forces Between Particles
     • Strong electrostatic forces of attraction between the electrons and positive nuclei of metal atoms
   • Properties
     • Conducts electricity
       • They have free electrons that are able to move and hence conduct a charge
     • Insoluble in water
       • The electrostatic forces between the particles are too strong to be overcome by the attractive forces between water and the metal
     • Malleable and Ductile
       • The non-directional attraction of the valence electrons means that metal atoms can slide past each other without breaking the overall structure
     • High melting and boiling point
       • There are strong electrostatic forces which require lots of energy to overcome
   • Structure
     • Free electrons from outer shell of metal atoms alternate with positive metal ions
   • Particles
     • Positive nuclei and delocalised electrons

2. Covalent Network

   • Properties
     • Do not conduct electroicty
       • They have no free electrons or ions
     • Usually Insoluble in water
       • Many molecular substances are not polar, since water is polar and like dissolves like, only polar substances will dissolve in water. Polarity is decided by the shape of the molecule (see structure)
     • Low melting and boiling point
       • The weak intermolecular forces do not require a lot of energy to overcome
   • Forces Between Particles
     • Weak intermolecular forces of attraction between the molecules
   • Particles
     • Molecules made up of atoms (strong intramolecular covalent bonds between these atoms)
   • Structure
     • 2 Regions of negative charge
       • Linear
     • 4 regions of negative charge
       • Two bonded, two non-bonded
         • Bent 4:
       • All bonded
         • Tetrahedral
       • Three bonded, one non-bonded
         • Trigonal Planer
     • 3 regions of negative charge
       • All bonded
         • Trigonal Planar
       • Two bonded, one non-bonded
         • Bent 3

3. Molecular

   • Particles
     • Atoms
   • Structure
     • 2D
       • 2D hexagonal layers. Within each layer the atom is bonded to three others, with delocalised electrons between the layers
     • 3D
       • 3D lattice where each atom is bonded to 4 others by strong covalent bonds.
   • Forces Between Particles
     • Strong covalent bonds between atoms
   • Properties
     • Graphite is soft
       • Layers are held together by weak bonds so can slide past each other
     • Diamond is hard
       • Strong covalent bonds makes the structure very rigid
     • High melting and boiling point
       • Strong covalent bonds so require lots of energy to overcome.
     • Diamond does not conduct, but graphite does.
       • Diamond does not have free electrons so does not conduct whereas graphite does

4. Ionic

   • Forces Between Particles
     • Strong electrostatic forces of attraction between oppositely charged ions
   • Structure
     • Regular 3D lattice structure consisting of alternating cations and anions
   • Particles
     • Negatively charged anions and positively charged cations
   • Properties
     • Conduct when molten or in solution
       • Electrons are removed from the rigid structure so can move and carry a charge
     • High melting and boiling points
       • Strong electrostatic forces of attraction so require large amounts of energy to overcome
     • Dissolve in polar solvents
       • The cations are attracted to the negative dipole whilst the anions are attracted to the positive dipole
     • Do not conduct in solid form
       • Electrons are fixed in the 3D lattice so cannot move or carry a charge