Covalent bonding

Covalent Molecular

  • Within molecules, atoms are held together by the electrostatic attraction between shared electrons and nuclei of atoms, forming covalent bonds
  • When atoms combine to form molecules, they often share electrons so that their outer shell has eight electrons
  • Electron dot diagrams can be drawn to show the formation of a molecule and to represent molecules
  • A single covalent bond is formed when two atoms share one pair of electrons
  • Covalent bonds are the strongest bonds
  • The atoms in the molecules are held together by strong covalent bonds
    • However, there are only weak attractive forces between each molecule, called intermolecular or van der Waals forces, because each molecule is electrically neutral
Property Explanation
Low melting and boiling points Forces between molecules are weak
Non-conductors of electricity The molecules are uncharged and the electrons are localised in covalent bonds or in the atoms
Solids are generally soft Forces between molecules are weak

Covalent Network

      • Every atom is covalently bonded to other atoms, forming a 3-D lattice
      • No separate molecule can be distinguished
      • Graphite, diamond and silicon dioxide
Property Explanation
Very high melting and boiling points Strong covalent bonding extending throughout the entire lattice
Non-conductors of electricity Electrons are localised in covalent bonds
Graphite is a good conductor Each pair of carbon atoms shares 3 of its electrons in layers, but the 4th is delocalised, allowing it to carry are charge
Hard and brittle Atoms strongly bonded; distortion causes the covalent bonds to break

 

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