Covalent+Bonds+and+Molecules

Covalent Bonding

Covalent Bonding is split into simple covalent structures and giant covalent structures. Simple Covalent Structures:
 * Covalent Bonding is the sharing of electrons between non-metallic elements so as to achieve the stable electronic configuration of a noble gas.
 * A covalent bond is the electrostatic attraction between the pair of negatively charged pair of shared electrons and the positively charged nuclei as a result of non-metallic atoms sharing electrons.
 * The atoms are bonded by strong covalent bonds and the molecules are then held together by weak van der Waals forces.
 * Simple Covalent Molecules generally have low mp/bp as very little energy is required to overcome the weak van der Waals forces between the molecules.
 * The degree of the intermolecular attraction is largely dependent on the size of the molecules. EG:Chlorine has stronger van der Waals forces as compared to Fluorine.
 * Larger molecules have more electrons and a greater distortion of electron cloud can be resulted.This gives rise to a stronger degree of van der Waals forces and more energy required to overcome the intermolecular attraction,thus resulting in higher mp/bp.
 * Melting/Boiling only overcomes the van der Waals forces.Covalent Bonds are NOT broken by melting/boiling.
 * Simple covalent molecules are poor electrical conductors at any states as there are no mobile ions/electrons. (Exceptions:Polar molecules which react with water to form ions,the aqueous solution conducts electricity because of the presence of mobile ions.)
 * Non-polar molecules are generally more soluble in non-polar solvents.Polar molecules are generally more soluble in polar solvents such as water.
 * Compounds with simple covalent molecules are soft because breaking of deforming the structure only requires the breaking of the weak intermolecular forces between molecules.
 * [[image:http://alevelnotes.com/content_images/i43_lewisCovalentBonding.gif]][]