(a(i))[1]
Complete these electronic configurations: cobalt atom, $\text{Co}$: $1s^22s^22p^6\ldots$ ; cobalt(II) ion, $\text{Co}^{2+}$: $1s^22s^22p^6\ldots$.
(a(ii))[5]
State the colours observed when concentrated $\text{HCl(aq)}$ is added to an aqueous solution of cobalt(II) nitrate, $\text{Co(NO}_3)_2$. Give the formulae and geometry of the complexes formed.
(b)[3]
Two isomers exist for the formula $\text{Ni(R}_3\text{P)}_2\text{I}_2$, whereas there is only one structure for $\text{Co(R}_3\text{P)}_2\text{I}_2$ ($R$ = alkyl, $\text{R}_3\text{P}$ is a monodentate ligand). Draw diagrams showing the structure of $\text{Co(R}_3\text{P)}_2\text{I}_2$ and the two isomers of $\text{Ni(R}_3\text{P)}_2\text{I}_2$.