Wednesday, 16 October 2013

Structures and Properties of Covalent Bonding

Covalent Bonding

  • A bond between two non-metal atoms. They bond by sharing electrons to complete their outer energy levels.
  • They are held together by strong forces of attraction of the shared electrons to the nuclei.
  • This can be expressed for molecules in diagrams:

e.g. Methane CH4

  • There are two types of covalent structures:
  1. Simple molecular structures
  2. Giant covalent structures

Simple Molecular Structures

  • Simple molecular structures are held together by weak intermolecular forces, formed when e- move towards one end of the atom.

Properties of Simple Molecular Structures

  • Low MP & BP - Weak intermolecular forces easily overcome
  • Does not conduct electricity
  • Does not dissolve in water, but may in some organic solvents.

Giant Covalent Structures

  • Held together by many strong covalent bonds, which require energy to break, meaning high MP & BP.
  • Graphite - Each carbon atom is bonded to three other carbon atoms.
  • The layers are held together by weak intermolecular forces - therefore soft, slippery substance
  • Graphite can be used as lubricant due to its structure.

  • Diamond - Each carbon atom has a complete outer energy level and is bonded to four other carbon atoms.
  • It is the hardest known substance, is used for cutting. It has a high MP due to the many strong covalent bonds.