covalent bonding

• Covalent bonding is the strong electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms
• Covalent bonding occurs between atoms in:

  • non-metallic elements
  • compounds of non-metallic elements
  • polyatomic ions
• For covalent bonding, the key feature is the sharing of a pair of electrons between the two atoms.

  The atoms are bonded together in a single unit:

  • a small molecule
  • a giant covalent structure
  • a charged polyatomic ion
• Covalent bond = the overlap of atomic orbitals, each containing one electron, to give a shared pair of electrons
• The shared pair of electrons in a covalent bond is attracted to the nuclei of both the bonding atoms.

  The bonded atoms often have outer shells with the same electron structure as the nearest noble gas
• The attraction in a covalent bond is localised, acting solely between the shared pair of electrons and the nuclei of the two bonded atoms
• A molecule is the smallest part of a covalent compound that can exist whilst retaining the chemical properties of the compound
• Paired electrons that are not shared in a covalent compound are called lone pairs
• Carbon forms 4 covalent bonds
• Nitrogen forms 3 covalent bonds
• Oxygen forms 2 covalent bonds
• Hydrogen forms 1 covalent bond
• Boron as three outer shell electrons so can only form 3 covalent bonds. In BF3, all three of its outer shell electrons are paired so BF3 only has 6 electrons around the boron atom. This shows that predictions for bonding cannot be based solely on the nearest noble gas electron structure