shapes of molecules and bonds

• electron pair repulsion:

  • the shape of a molecule is caused by repulsion between the pairs of electrons ( both bond and lone pairs)
  • electron pairs arrange themselves so that repulsion is at a minimum
• in order to determine the shape of a molecule containing one or more multiple bonds, treat each multiple bond as if it only contained one pair of electrons
• Shape: Linear

  Bond pairs: 2

  Lone pairs: 0

  A) 180

  
• Shape: trigonal planar

  Bond pairs: 3

  Lone pairs: 0

  A) 120

  
• shape: tetrahedral

  bond pairs: 4

  lone pairs: 0

  A) 109.5

  
• shape: trigonal bipyramid

  bond pairs: 5

  lone pairs: 0

  A) 90

  B) 120

  
• shape: octahedral

  bond pairs: 6

  lone pairs: 0

  A) 90

  
• shape: trigonal pyramidal

  bond pairs: 3

  lone pairs: 1

  A) 107

  
• shape: V-shaped

  bond pairs: 2

  lone pairs: 2

  A) 104.5

  
• lone pair-bond repulsion is greater than bond-pair repulsion so if there are lone pairs the angle will be smaller
• if there is a lone pair in a shape the angle will be 2.5 degrees less than the bond angle