Complex ions Transition metals can form complexes because their ions have a high charge density: o they have quite a large nuclear charge but are relatively small; o the 3d electrons are not so effective (as 2s or 2p electrons) at shielding the effect of the ionic charge which really comes from the nucleus. This allows the transition metal ions to have a great polarising power and they can attract lone pairs from other atoms to form complexes.

Complex ions Ions formed by a metal ion to which a number of ligands (molecules and/or negative ions) are bonded using a dative bond Ligand = molecule or negative ion with a non- bonding pair of electrons which is used to make a dative bond Example: [Fe(H 2 O) 6 ] 3+ Coordination number is the number of ligands that surround the metal ion

More examples complex ions [Fe(CN) 6 ] 3- [CuCl 4 ] 2- [Cu(NH 3 ) 4 ] 2+ [Ag(NH 3 ) 2 ] + Charge on the ion is the sum of all charges. Work out the charge of each metal ion in the complexes above.

Naming complex ions ligandnumber H 2 O - aqua1 - mono OH - - hydroxo2 - di NH 3 - ammine3 - tri Cl - - chloro4 - tetra Br - - bromo5 - pent CN - - cyano6 – hex You name the ligand and its number first before naming the metal. You use the name of the metal if the ion is positive but use –ate ending if negative e.g. ferrate, cuprate, vanadate.

Shapes complex ions Depends on coordination number If 6 then shape = octahedral If 4 then shape = tetrahedral (or square planar = less common) If 2 then shape = linear

Shapes of complex ions

Coloured complex ions

Coloured Cu 2+

Coloured ions

Factors affecting colour nuclear charge oxidation state of ion (i.e. number of electrons) ligand coordination number shape of the complex

Colour complex ions