Shapes of molecules

  • According to the valence shell electron pair repulsion theory (VSEPR), electron pairs in the outer shell of an atom repel each other and are arranged as far apart as possible.
  • This allows for the prediction of the arrangement of molecules and atoms.
  • Please note that you must show lone pairs of electrons.
  • Lone pairs of electrons exert greater force than bonds
  • Single bonds and double bonds exert approximately the same amount of force.
Shape Representation Description Examples
Linear (2)   linear molecule All diatomic molecules are linear. Molecules with only two areas of negative charge around the centre are linear. All two are bonding pairs. H2HCl

BeF2

Trigonal Planar (3)  trigonal planar molecule Three areas of negative charge will arrange themselves around the central atom, all in the same plane. All three are bonding pairs of electrons. BCl3
Tetrahedral (4)  tetrahedral molecule Four areas of negative charge surround the central atom, only two in the same plane. All four are bonding pairs. CH4SiF4
Trigonal pyramid (4)  trigonal pyramid molecule Although there are four areas of negative charge, one of them is a non-bonding pair of electrons.  NH3
V-shaped (4)  bent molecule Four areas of negative charge, but 2 lone pairs. Bond angles are as above. H2OSBr2
V-shaped (3 pairs) or planar  v-shaped molecule Three areas of negative charge, but with one lone pair, as the lone pair pushes the other two closer together. The three pairs are on the same plane.  SO2

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