Complete the electronic configurations for a Co atom and a $\text{Co}^{2+}$ ion. Co atom $1s^22s^22p^6$ ................. $\text{Co}^{2+}$ ion $1s^22s^22p^6$ .................
What does the term complex ion mean?
Draw the tetrahedral complex ion made by one $\text{Co}^{2+}$ ion and four $\text{Cl}^-$ ions. Your drawing should clearly show the three-dimensional shape and should state the overall charge on the ion.
Explain why many transition metal complexes have colour.
Using ideas from your answer to (iii), suggest why the complex formed from one $\text{Co}^{2+}$ ion and four $\text{Cl}^-$ ions is blue.
Describe the colour change that happens when water is added to blue crystals of the cobalt(II)-chloride complex. Name the type of reaction responsible for this colour change. colour change ............. type of reaction .............
In this reaction, $\text{Co}^{2+}(aq)$ is oxidised to $\text{Co}^{3+}(aq)$. Use the Data Booklet to suggest one suitable oxidising agent for this reaction.
Calculate the $E^\circ_{\text{cell}}$ for this reaction.
Write an equation for the reaction of $\text{Co}^{2+}$ with the oxidising agent you chose in (d)(i).
Cobalt(III) can form two octahedral isomers with the formula $[\text{Co(NH}_3)_3(\text{NO}_2)_3]$. The $\text{NO}_2^-$ ion is monodentate. Complete the diagrams to show the three-dimensional structures of the two isomers, and name the type of isomerism shown here.