Write the electronic configuration for an isolated gaseous nickel(II) ion, $\text{Ni}^{2+}$.
Explain how colour arises in transition element complexes.
Hexaaquanickel(II) ions are green. In equilibrium 1 they produce a green precipitate with hydroxide ions, $\text{OH}^-$, and in equilibrium 2 they form a blue complex with ammonia, $\text{NH}_3$. $[\text{Ni(H}_2\text{O})_6]^{2+} + 2\text{OH}^- \rightleftharpoons \text{Ni(OH)}_2 + 6\text{H}_2\text{O}$. $[\text{Ni(H}_2\text{O})_6]^{2+} + 6\text{NH}_3 \rightleftharpoons [\text{Ni(NH}_3)_6]^{2+} + 6\text{H}_2\text{O}$. Use Le Chatelier’s principle to explain why a green precipitate appears when aqueous $\text{NH}_3$ is added dropwise to $[\text{Ni(H}_2\text{O})_6]^{2+}$.
Explain why the green precipitate dissolves and a blue solution appears when a large excess of aqueous $\text{NH}_3$ is added to $[\text{Ni(H}_2\text{O})_6]^{2+}$.
Hexaaquanickel(II) ions are green. In equilibrium 1 they form a green precipitate with hydroxide ions, $\text{OH}^-$, and in equilibrium 2 they make a blue complex with ammonia, $\text{NH}_3$.\n\nEquilibrium 1:\n$\left[\text{Ni(H}_2\text{O})_6\right]^{2+} + 2\text{OH}^- \rightleftharpoons \text{Ni(OH)}_2 + 6\text{H}_2\text{O}$ (green precipitate)\n\nEquilibrium 2:\n$\left[\text{Ni(H}_2\text{O})_6\right]^{2+} + 6\text{NH}_3 \rightleftharpoons \left[\text{Ni(NH}_3)_6\right]^{2+} + 6\text{H}_2\text{O}$ (blue)\n\nApply Le Chatelier’s principle to give explanations for the observations below.
The complex ion $[\text{NiBr}_2(\text{CN})_2]^{2-}$ exhibits stereoisomerism. Draw diagrams to show the two isomers of $[\text{NiBr}_2(\text{CN})_2]^{2-}$. Name the type of stereoisomerism.