Shapes of molecules and ions

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Created by
Harry

Cards (6)

  • Representing 3D shapes
    • Solid line - represents a bond in the plane of the page.
    • Solid wedge - represents a bond coming out of the page towards you
    • Dotted wedge - represents a bond going into the page away from you
  • Electron pair repulsion theory
    • The number if electron pairs around a central atom determines the shape of the molecule or ion
    • The electron pairs repel one another so that they are arranged as far apart as possible
    • The arrangement of electron pairs minimises repulsion and holds the bonded atoms in a definite shape
    • Different numbers of electron pairs results in different shapes
  • Shapes of molecules- 2, 3 and 4 pairs
    2 bonding electron pairs- Linear 180°
    3 bonding electron pairs- Trigonal planar 120°
    2 bonding and 1 lone electron pairs- Bent 117.5°
    4 bonding electron pairs- Tetrahedral 109.5°
    3 bonding and 1 lone electron pairs- Trigonal pyramidal 107°
    2 bonding and 2 lone electron pairs- Bent 104.5°
  • Shapes of molecules- 5 and 6 pairs
    5 bonding electron pairs- Trigonal bipyramidal 120° 90°
    4 bonding and 1 lone electron pairs- Trigonal pyramidal or see-saw 119° 89°
    3 bonding and 2 lone electron pairs- Trigonal planar or T-shape 120° or 89°
    6 bonding electron pairs- Octahedral 90°
    5 bonding and 1 lone electron pairs- Square pyramid 89°
    4 bonding and 2 lone electron pairs- Square planar 90°
    3 bonding and 3 lone electron pairs- T-shape 90°
  • Working out shapes of molecules(VSEPR)
    1. Identify central atom and identify how many outer electrons it has
    2. Work out how many electrons are shared by surrounding atoms
    3. Add an electron if negatively or remove an electron if positively charged central atom
    4. Add up all of the electrons in pairs and divide by two to work out number of electron pairs
  • Working out shapes with double or triple bonds
    1. Identify central atom and identify how many outer electrons it has
    2. Work out how many electrons are shared by surrounding atoms
    3. Add an electron if negatively or remove an electron if positively charged central atom
    4. Add up all of the electrons in pairs
    5. Minus two electrons for each double bond or minus 4 electrons for each triple bond this treats the bonds as single bonds.
    6. Divide the number of electrons by two to work out number of electron pairs