Ch 8 - Bonding

Type of bonding: Formed between: Held together by: Properties:

delocalized electrons (electrostatic attratction) Type of bonding: Formed between: Held together by: Properties: Metallic Two metals delocalized electrons Very high melting point Solid at room Temp Conducts heat and electricity Malleable Ductile Reacts with acid Ionic Metal and a non-metal (cation and anion) Transfer of electrons (electrostatic attratction) High melting point Solid at room temp (form crystals) Dissolves in water Conducts electricity when dissolved in water Brittle Covalent Two non-metals Sharing of electrons solid, liquid or gas at room Temp Does not dissolve in water Does not conduct electricity in any form Low melting points

Intermolecular forces of attraction Intermolecular forces of attraction are forces between different molecules. The intermolecular forces of attraction considered here are: Van der Waals' forces permanent dipole-permanent dipole interactions hydrogen bonding

Van der Waals' forces are forces of attraction which exist between all atoms and molecules. Van der Waals' forces are much weaker than all other types of bonding. They are only significant in atoms and molecules which have no other types of intermolecular forces of attraction, for example, discrete non-polar molecules and the Group 0 elements. Van der Waals' forces are a result of electrostatic attraction between temporary dipoles and induced dipoles caused by movement of electrons in atoms and molecules.

Permanent dipole-permanent dipole interactions are additional electrostatic forces of attraction between polar molecules. Permanent dipole-permanent dipole interactions are stronger than Van der Waals' forces for molecules of equivalent size.

Hydrogen bonds are permanent dipole-permanent dipole interactions. Bonds consisting of a hydrogen atom bonded to an atom of a strongly electronegative element such as fluorine, oxygen or nitrogen are highly polar. Hydrogen bonds are electrostatic forces of attraction between molecules which contain these highly polar bonds.