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Complex ions. Transition metals can form complexes because their ions have a high charge density: they have quite a large nuclear charge but a re relatively small ;
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Complex ions • Transition metals can form complexes because their ions have a high charge density: • they have quite a large nuclear charge but are relatively small; • 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(H2O)6]3+ • Coordination number is the number of ligands that surround the metal ion
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
Factors affecting colour • nuclear charge • oxidation state of ion (i.e. number of electrons) • ligand • coordination number • shape of the complex
