Explain the following

${\mathrm{BF}}_3$ has no dipole moment, but ${\mathrm{PF}}_3$ has a substantial dipole.

Explain the following 

${\mathrm{BF}}_3$ and ${\mathrm{BrF}}_3$ molecules have different shapes.

Give equations to show the reactions between $\mathrm{Al}$ and ${\mathrm{N}}_2$.

Give equations to show the reactions between $\mathrm{Al}$ and ${\mathrm{O}}_2$.

Give equations to show the reactions between $\mathrm{Al}$ and ${\mathrm{Cl}}_2$.