Covalent page

Covalent bonding
Some elements tend neither to lose nor to accept valence electrons. They achieve the stable electron configuration of a noble gas by sharing electrons.

A pair of shared electrons forms a single covalent bond. A set of atoms linked together with covalent bonds is called a molecule.

The formation of covalent bonds can be illustrated by Lewis dot structures.

Animations
1. [[media:h2.swf|The hydrogen molecule]] 2. [[media:HCl.swf| The hydrogen Chloride]] 3. [[media:H2O.swf| The Water molecule]] 4. [[media:CH4.swf| The Methane molecule]] 5. [[media: Cl2.swf| The Chlorinemolecule]]

View the [[media:lewis.swf| Lewis]] dot and cross diagram

Sigma and pi bond


The various atomic orbitals which are pointing towards each other now merge to give molecular orbitals, each containing a bonding pair of electrons. Molecular orbitals made by end-to-end overlap of atomic orbitals are called sigma bonds.

This sideways overlap also creates a molecular orbital, but of a different kind. In this one the electrons aren't held on the line between the two nuclei, but above and below the plane of the molecule. A bond formed in this way is called a pi bond In ethene the first bond is a sigma bond while the second bond is a pi bond.

To view examples of molecules having sigma and pi bonds [[media:pi&sigma.swf|click here]]