The $3d$ orbitals of an isolated $\text{Fe}^{2+}$ ion are degenerate. Finish the diagram to illustrate how the $3d$ orbital energy levels split first in an isolated $\text{Fe}^{2+}$ ion and then when $\text{Fe}^{2+}$ forms an octahedral complex.
Bipyridine, bipy, acts as a bidentate ligand. Explain what is meant by bidentate ligand.
Complete the three-dimensional diagrams to show the two stereoisomers of $[\text{Fe(bipy)}_3]^{2+}$. State the type of stereoisomerism shown. Use the symbol given to represent bipy in your diagrams.
Use suitable data from Table 4.1 to state which iron(III) complex is hardest to reduce. Explain your answer.
Using the hybridisation of the carbon atoms and the nitrogen atom, and orbital overlap, suggest how the $\sigma$ and $\pi$ bonds form in a pyridine molecule.
Complete the diagram to show the mechanism for the reaction of pyridine with $\text{Cl}^+$. Include every relevant charge, dipole, lone pair of electrons and curly arrow as appropriate.