covalent bonding

• covalent bonding - atoms share pairs of electrons

  • can be giant covalent structures e.g polymers
  • can be small molecules e.g ammonia
• simple covalent bonds have low melting and boiling points because they have weak intermolecular bonds (little energy to overcome)
• covalent bonds inside a molecule are very strong
• as the molecules get bigger, the strength of the intermolecular forces increases
• molecular compounds don't conduct electricity because they don't have any free electrons or ions
• dot and cross

  
• dot and cross

  • shows which atom the electron in the bond comes from
  • all electrons look identical
• 2d with bonds

  • shows which atoms are bonded together
  • shows the bond incorrectly at 90 degrees
• 3d ball and stick model

  • attempts to show the bond at 109.5 degrees