1g - covalent bonding

• Covalent bonding


  Bonding between non-metals by sharing pairs of electrons
• Covalent bonding


  • Atoms can bond by sharing valence electrons to achieve a stable outer shell configuration
  • Only the outer shell electrons are involved in bonding
• Covalent bond


  The electrostatic attraction between the shared pair of electrons and the positive nuclei of the bonding atoms
• How to draw dot and cross diagrams for simple molecular structures


  1. Write the formula first

  2. Look at the electronic configuration and work out how many bonds each atom needs to make

  3. Arrange the atoms around each other - any that only make one bond will be on the outside, ones that make more than one go in the middle

  4. Draw the central atom surrounded by the other atoms, add the shared electron pairs in the overlap areas
• Bonding within molecules


  • Strong covalent bonds
  • Weak intermolecular forces between molecules
• Simple molecular covalent structures


  • Have low melting and boiling points because only weak intermolecular forces need to be broken
  • Have higher melting and boiling points than smaller simple molecules because more intermolecular forces need to be broken
• When a simple covalent substance melts or boils, the covalent bonds within the molecules remain intact, only the intermolecular forces are broken
• Simple covalent structures don't conduct electricity because there are no free electrons
• Giant covalent structures


  • 3D, infinite, lattice structures
  • Strong covalent bonds between all the atoms
• Diamond = hard because they have strong forces of attraction, they are used for glass cutting and drilling rocks
• graphite = soft because it has weak forces of attraction and their layers slide over each other uses are pencils and electrodes
• sublimes = solid to gas without being a liquid
• diamond doesn't conduct electricity because it has no delocalised electrons
• graphite conducts electricity because it has delocalised electrons which are free to move and carry charge
• diamond = 3D giant covalent structure
• Graphite - 2D giant covalent layers#
• Fullerene - simple molecular structure
• Diamond and graphite has a high melting point because for their strong covalent bonds to be broken it requires a lot of energy in the form of a high temperature
• Fullerene - has a low melting point because it takes less energy/heat to break the inter molecular forces between the molecules