Describe the general trends in the ionisation enthalpy of the elements in Groups $13$ and $14$.

Describe the general trends in the following property of the elements in Groups $13$ and $14$.

Metallic character

Describe the general trends in the following property of the elements in Groups $13$ and $14$.

Oxidation states

Describe the general trends in the following property of the elements in Groups $13$ and $14$.

Nature of halides

Account for the following observation:

${\mathrm{AlCl}}_3$ is a Lewis acid

Account for the following observations:

Fluorine is more electronegative than chlorine yet ${\mathrm{BF}}_3$ is a weaker Lewis acid than ${\mathrm{BCl}}_3$.

Account for the following observation:

${\mathrm{PbO}}_2$ is a stronger oxidising agent than ${\mathrm{SnO}}_2$

Account for the following observation:

The $+1$ oxidation state of thallium is more stable than its $+3$ state.