Complex ions

• ·         All transition metal ions can form co-ordinate (dative) covalent bonds by accepting electron pairs from other ions or molecules (ligands).
• ·         The number of co-ordinate bonds to ligands surrounding the central ion is called the co-ordination number.
• ·         Aqua ions are where a positively charged metal ion is surrounded by water molecules acting as ligands.
• ·         Multidentate ligands are molecules or ions that have more than one atom with a lone pair of electrons that can create a dative bond with a central transition metal ion, with chelates being the complex ions with polydentate ligands formed.
• ·         The chelate effect is the idea that chelate complexes with polydentate ligands are favoured over monodentate ones as it leads to an increase in the number of particles produced and therefore increases entropy.
• ·         Complex ions follow the same shape rules as previously seen molecules, being represented with wedge and dash diagrams.
• ·         Transition metal complexes can form both geometric and optical isomers.