Explain the meaning of the term transition element.
Describe the colour change observed when excess of $\text{Sn}^{2+}(aq)$ is added separately to dilute acidified $\text{MnO}_4^{-}(aq)$ and to dilute acidified $\text{Cr}_2\text{O}_7^{2-}(aq)$.
Write an equation showing the reaction of $\text{Sn}^{2+}(aq)$ with acidified $\text{Cr}_2\text{O}_7^{2-}(aq)$.
State the meaning of a co-ordination number of six.
State the formula for $X$. Be sure to include its charge.
Draw the two isomeric forms of $X$. Your diagrams should show the three-dimensional shapes of the two isomers and how each ligand is attached to the central ruthenium ion.
Suggest which type of isomerism is shown by $X$.
Explain how colour arises in a transition element complex such as $X$.