Complete the electron configurations of Ni and $\text{Ni}^{2+}$.
The $d$ orbitals in an isolated transition metal atom or ion all have the same energy. What name is given to orbitals with equal energy?
Complete the diagram to show how the $d$ orbital energy levels split in an octahedral complex ion.
On the axes below, sketch the shapes of one $d$ orbital from the lower-energy level and one $d$ orbital from the higher-energy level.
The octahedral complex $[\text{Ni(H}_2\text{O)}_6]^{2+}$ is green. Explain where the colour of this complex comes from.
When $\text{NH}_3\text{(aq)}$ is added to the green solution containing $[\text{Ni(H}_2\text{O)}_6]^{2+}$, a grey-green precipitate, A, forms. This precipitate dissolves in excess $\text{NH}_3\text{(aq)}$ to produce a blue-violet solution, B. Suggest formulae for A and B, and write equations for the two reactions that form A and B.