Shapes of molecules and ions - 2

HideShow resource information
  • Created by: Shannon
  • Created on: 08-05-14 08:49
View mindmap
  • Shapes of molecules and ions
    • Electron pair repulsion theory
      • The type of electron pairing affects how much repulsion is experienced
        • Lone pair/lone pair bond angles are the biggest
        • Lone pairs repel more than bonding pairs
        • Bond angles between bonding pairs are reduced because they are pushed together by lone-pair repulsion
    • Characteristic shapes
      • 2 electron pairs on the central atom
        • Linear
          • e.g BeCl2
        • Bond angle of 180
      • 3 electron pairs on central carbon
        • No lone pairs
          • Trigonal planar
            • e.g BCl3
          • Bond angle of 120
        • 1 lone pair
          • Bent
            • e.g CO2
          • Bond angle of 120
      • 4 electron pairs on central atom
        • No lone pairs
          • Tetrahedral
            • e.g CH4
          • Bond angle of 109.5
        • 1 lone pair
          • Trigonal pyramidal
            • e.g NH3
          • Bond angle of 107
        • 2 lone pairs
          • Bent
            • e.g H2O
          • Bond angle of 104.5
      • 5 electron pairs on central carbon
        • Trigonal bipyramidal
          • e.g PCl5
        • Bond angles of 90 and 120
      • 6 electron pairs on central carbon
        • Octahedral
          • e.g SF6
        • Bond angles of 90
    • Carbon structures
      • Carbon forms three allotropes
        • Different forms of the same element in the same state
        • Diamond
        • Graphite
        • Fullerenes
      • Diamond
        • The carbons in diamond are covalently bonded, with sigma bonds, to 4 other carbon atoms
        • Atoms are arranged in a tetrahedral shape
          • Crystal lattice structure
        • Has a very high melting point
        • Extremely hard
          • Used in diamond-tipped drills and saws
        • Good thermal conductor
          • Vibrations travel easily through the lattice
      • Graphite
        • Carbon atoms are arranged in sheets of flat hexagons, covalently bonded with 3 bonds
          • The 4th outer electron is delocalised
        • The weak bond between layers are easily broken, so that the sheets can slide over each other
          • Used in dry lubricant and in pencils
        • Electrical conductors
          • Delocalised electron free to move
        • The layers are far apart in comparison to the length of the covalent bonds
          • This means that it is less dense than diamond
            • Used for strong, lightweight sports equipment
      • Fullerenes
        • Molecules of carbon shaped like hollow balls or tubes
        • Each carbon atom forms 3 covalent bonds, leaving free electrons that can conduct electricity
        • Because they are hollow, they can be used to cage other molecules
          • Form around another molecule, trapping it inside
          • Could be used to deliver a drug into specific cells of the body
        • Nanotubes
          • Single layer of graphite rolled into a hollow tube
            • Very strong, due to covalent bonding
              • Used to reinforce graphite and to make stronger, lighter bulding materials
              • Can conduct electricity
                • Used in circuits for computer chips

Comments

No comments have yet been made

Similar Chemistry resources:

See all Chemistry resources »See all Bonding & shapes resources »