Shapes of Molecule

• Single bonds

  • Single bond is a sigma bond between two atoms and is the sharing of one pair of electrons.
• Double bond

  • a Pie-bond is formed by two p-orbital overlapping, do that the overlap lies above and below the line joining the centres of the 2 atoms.
  • a double bond consist of a sigma and a pie bond between two atom

  
• Lone pairs and bond pairs

  • a pair of electrons in a covalent bond are called bonding pair.
  • pairs of electrons that are not involved in bonding are called lone pairs
  • electrons pairs are cloud of negative charge, so there is mutual repulsion between them, forcing them as far apart as possible
• Describing shaped of molecules

  1. Bond length is the distance between the nucleic of two bonded atoms
  2. bond angles is the angle between 2 covalent bonds
• Effect of lone pairs on shape

  Greatest repulsion: Lp-Lp

  Normal repulsion: Lp-Bp

  Least repulsion: Bp-Bp
• Steps to work out the shape of a molecule:

  1. What group is the central element in
  2. Is the molecule charged
  3. How many covalent bonds are there (double or single)
  4. What is the total number of eletrons
  5. How many electron pairs are there? Are there lone pair
  6. What is the basic shape