COVALENT BONDING

COVALENT BONDING

1. bond length: single < double < triple

2. bond strength: single < double < triple

3. use VSEPR to predict the shapes of molecules

   • pairs of valence electrons repel each other and will take up positions to minimise these repulsions
   • lone pairs repel more than bonding pairs

4. giant covalent compounds

   • have high melting points because covalent bonds are broken when melting
   • Examples
     • silicon
     • SiO2
     • diamond
     • graphite

5. covalent molecular compounds

   • non-polar molecules
   • polar molecules
     • difference in electronegativity: electrons lie more towards one atom than another
     • shape of molecules: if the dipole moments of individual bonds cancel, the molecule is not polar
   • only intermolecular forces are broken when melting
     • Van der Waals forces caused by instantaneous and induced dipoles
     • dipole-dipole forces
     • hydrogen bonds

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