1.3 Bonding

• ionic bonding

  electrostatic attraction between oppositely charged ions in a lattice
• covalent bond

  shared pair of electrons between a metal and non metal
• dative covalent bond

  shared pair of electrons, with both electrons coming from 1 atom
• metallic bonding

  electrostatic attraction between delocalised electrons and positive ions in a lattice
• simple molecular (iodine)

  covalent bonds

  weak vdw forces - low mp, bp
• diamond

  4 carbons

  strong covalent bonds -> high mp

  no electricity
• graphite

  3 carbons - flat sheet

  delocalised e- - move between layers

  strong covalent bonds -> high mp

  electricity - delocalised e- carries charge
• ionic (sodium chloride)

  high mp, bp -> strong electrostatic forces

  molten or aqueous - conduct electricity - ions free to move

  brittle
• metallic (Al)

  good conductors - carry charge

  malleable - layer of +ve ions slide over eachother

  high mp

  solid at room temp (except mercury)
• lone pair repulsion

  electrons in the outer shell arrange themselves as far apart as possible to minimise repulsion
• electronegativity


  power of an atom to attract a pair of electrons in a covalent bond
• electronegativity factors

  increases along a period -> atomic radius decreases

  decreases down a group -. shielding increases
• polar molecule

  unequal sharing of electrons between elements with different electronegativitys -> permanent dipole
• 2 electron pairs - linear, 180
• 3 electron pairs - triagonal planar, 120


  [2,1] bent v shape, 118
• 4 electron pairs - tetrahedral, 109.5


  [3,1] triagonal pyramidal, 107

  [2,2] bent v shape, 104.5
• 5 electron pairs - triagonal bipyramidal, 90 120


  [4,1] triagonal pyramidal, 89 119

  [3,2] triagonal planar, 89, 120
• 6 electron pairs - octahedral, 90

  [5,1] square pyramid, 89

  [4,2] square planar, 90