what is meant by the term "transition metal" and illustrate your answer by comparing mercury (which is not a transition metal) with vanadium. Define the terms "ligand" and "complex ion", illustrated with examples. Give examples of transition metal complex ions formulae, using and explaining square bracket notation, and draw 3D diagrams of "octahedral", "tetrahedral" and "square planar" shaped complexes. Use this information to describe the main features of transition metal complex ions, with particular reference to the bonding within the complex ion