(a)[1]
Explain why transition elements exhibit variable oxidation states.
(b)[1]
Sketch the shape of a $3d_{xy}$ orbital.
(c)[3]
Explain why transition elements produce coloured compounds.
(d(i))[1]
State the colour shown by $\text{Cu(OH)}_2(s)$ and by $[\text{Cu(NH}_3)_4(\text{H}_2\text{O})_2]^{2+}(aq).
(d(ii))[1]
Use Le Chatelier’s principle to explain why a precipitate appears when $\text{NaOH}(aq)$ is added dropwise to $[\text{Cu(H}_2\text{O})_6]^{2+}(aq)$.
(e)[2]
The formula $[\text{Cu(NH}_3)_4(\text{H}_2\text{O})_2]^{2+}$ can exist as two stereoisomers. Draw three-dimensional diagrams to show the two stereoisomers.