Chemical Bonding

Covalent Bond

Metallic Bond

Ionic bond

Giant metallic lattice structure

  • strong electrostatic forces of attraction between delocalised electrons and the metal cation
  • non-directional bonding pattern

Pure Metals

Alloys

high melting points

  • giant metallic lattice structure
  • large amounts of energy is required to overcome bond

good electrical conductors

  • presence of positive ions surrounded by delocalised electrons
  • delocalised electrons act as charge carriers to conduct electricity under the influence of a potential difference
  • conductivity increases from Na to Al (Al has the greatest number of delocalized electrons)

strong metals

  • atoms are of different sizes --> break up the regular arrangement of the atoms in pure metals
  • layer of atoms in alloys cannot slide over each other easily when force is applied

lower melting point then pure metal

  • melt over a range of temperatures

good electrical conductor

  • prescence of delocalised ions

uses of alloys

  • make metals stronger and harder
  • lower melting points
  • more resistant to corrosion

malleable and ductile

  • electrons do not belong to a particular metal atom
  • layer of positive ions slides over the other without disrupting the metallic bond

Simple molecular Structure

  • strong covalent bonds between atoms
  • weak intermolecular forces between molecules

Giant Covalent Bond

  • strong covalent bond between atoms

giant ionic lattice structure
strong electrostatic forces of attraction between cations and anions
non-directional bonding

good electrical conductivity

  • only in molten or aqueous states
  • (bonding) is overcome
  • ions are free to move around
  • electricity can be conducted by mobile ions

Hard but Brittle

  • ions with similar charge from neighbouring layers face each other
    repulsive force between similar charges spilts crystals

intermolecular forces

low melting and boiling points

  • small amt of energy needed

Van der Waals' forces

  • temporary dipole --> present in all molecules
  • permanent dipole --> present in polar molecules

Hydrogen Bond

  • molecules with F-H, O-H AND N-H
  • stronger than Van der Waals' forces

poor electrical conductivity

  • do not contain mobile ions or delocalised electrons to act as charge carriers to conduct electricity
  • exceptions: strong acids, polar molecules, graphite

insoluble in water

  • except for polar molecules
  • ability of molecules to form hydrogen bonds with each other

high melting and boiling points

  • large amt of energy needed to overcome strong covalent bonds between atoms

Diamond

  • bonded tetrahedrally to 4 other carbon atoms

Graphite

  • made up of hexagonal layers
  • within each layer, each C forms strong covalent bonds w 3 other C --> hexagonal ring

very hard

  • difficult to break bonds

soft and slippery

  • layer of C are held loosely by weak intermolecular forces of attraction
  • C slides over each other when force applied

does not conduct electricity

  • all outer shell electrons are used
  • no delocalised electrons

able to conduct electricity

  • one valence e per C not used
  • delocalised electrons along the same plane can conduct electricity

soluble in water, insoluble in organic solvent

high melting and boiling point