How can you explain the higher stability of ${\mathrm{BCl}}_3$ as compared to ${\mathrm{TlCl}}_3$?

Why does boron trifluoride behave as a Lewis acid?

Is boric acid a protic acid? Explain.

Explain what happens when boric acid is heated.

Describe the shapes of ${\mathrm{BF}}_3$ and ${{\mathrm{BH}}_4}^{–}$. Assign the hybridisation of boron in these species.

Write reactions to justify the amphoteric nature of aluminium.

Write the resonance structures of ${{\mathrm{CO}}_3}^{2–}$and ${{\mathrm{HCO}}_3}^{–}$.