Describe three typical chemical properties of transition elements that are not shown by Group II elements.
When $\text{NH}_3(aq)$ is added to a green solution containing $\text{Ni}^{2+}(aq)$ ions, a grey-green precipitate appears. This solid then dissolves in excess $\text{NH}_3(aq)$ to produce a blue-violet solution. Suggest an explanation for these results, showing your reasoning and including equations for the reactions described.
Dimethylglyoxime, DMG, is a useful reagent for the quantitative estimation of nickel. It forms an insoluble salt with nickel ions, as shown below. $\text{Ni}^{2+}(aq) + \text{C}_4\text{H}_8\text{N}_2\text{O}_2(aq) \rightarrow \text{NiC}_4\text{H}_6\text{N}_2\text{O}_2(s) + 2\text{H}^+(aq)$ A small coin with a mass of $3.40\,\text{g}$ was dissolved in nitric acid, and an excess of DMG was added. The resulting Ni-DMG precipitate was filtered, washed and dried. Its mass was $4.00\,\text{g}$. Calculate the percentage of nickel in the coin.