2.3 Molecular Compounds Bonding and Properties LO: I understand how the bonding present affects the physical properties of a molecular substance.

In covalent molecular substances the covalent bonds are confined to the individual molecules. In covalent molecules like CF 4 : hold the atoms together., hold the molecules together. The physical properties depend on the, forces and not the covalent bonds. LO: I understand how the bonding present affects the physical properties of a molecular substance. Covalent bonds Weak van der Waals forces intermolecular

2.3.2Effect of Increasing Atomic Size LO: I understand how the atomic size affects the physical properties of carbon tetrahalides.

Melting point vs covalent radius of halogen: As the size increases the melting point. Covalent Radius (picometres) Melting Point (˚C) CF 4 CCl 4 CBr 4 CCI 4 This is because the increase in strength with atomic size. LO: I understand how the atomic size affects the physical properties of carbon tetrahalides. increases van der Waals forces

2.3.3Effect of Increasing the Number of Atoms LO: I understand how the number of atoms affects the physical properties of the alkanes.

Boiling point of the alkanes: As the number of atoms increases the boiling point. This is because the are increasing in number. LO: I understand how the number of atoms affects the physical properties of the alkanes. Boiling Point (˚C) Number of carbon atoms C3H8C3H8 C 4 H 10 C 5 H 12 C 6 H 14 C 7 H 16 C 8 H increases van der Waals forces