(a)[1]
Element $Q$ has the electronic configuration $[\text{Ar}]\,3d^2\,4s^2$. Predict the oxidation states that are likely for element $Q$ in compounds.
(b)[1]
Suggest why transition elements frequently exhibit variable oxidation states in their compounds, whereas ordinary $s$-block elements such as calcium do not.
(c)[3]
Many enzymes contain transition element complexes. Describe, using a suitably labelled diagram, how an enzyme catalyses the breakdown of a substrate molecule.