transition metals

• The elements from titanium to copper are metals. So their characteristics include being good conductors of heat and electricity. They are hard, strong, and shiny, with high melting and boiling points. These physical properties, combined with low chemical reactivity makes these metals extremely useful.
• The metals from titanium to to copper are also transition metals, so have variable oxidation states, form coloured ions, make useful catalysts and form complex ions. This is as they form at least one stable ion with a partly full d orbital.
• Zinc and Scandium are not transition metals as they do not form any ions with partly filled d orbitals, they are however d block elements
• d block elements have similar properties as they have similar electron configurations. Excluding copper and cronium (which favour half or fully filling their 3d orbital for stability) they all have full 4s orbitals. And as you move across the period electrons are added to the inner 3d orbital.
• Ligand: A ion or molecule with a lone pair of electrons, that forms a co-ordinate bond with a transition metal.
• co-ordinate bond: When an ion or molecule donates an electron pair, forming a covalent bond.
• co-ordination number: The number of co-ordinate bonds to ligands that surround the d-block metal ion
• ions with a co-ordination number six are usually octahedral
• ions with the co-ordination number four are usually tetrahedral
• ions with the co-ordination number four are sometimes square planar
• aqua ions- when you dissolve a transition metal in water, the positively charged metal ion is typically surrounded by six water molecule ligands in octahedral arrangements
• bidentate ligands: molecule with two atoms in their structure that have a lone pair of electrons that bond to the transition metal ion
• multidentate ligands: have more than two atoms in the structure with a lone pair of electrons, that can bond to the transition metal ion
• the chelate effect: A chelate is a complex ion with polydentate ligands. If you add a hexadentate ligand to a transition metal salt solution, you can remove all water ligands from the salt. Chelate complexes with polydentate ligands are favoured over complex with monodentate ligands, as the increase in the number of particles causes an increase in the entropy.
• the shape of a complex ion with six ligands is octahedral as although ther are only 6 bonds the complex has 8 faces when pictured in 3D
• The size of ligands affects how many can fit around the central atom. Fewer of a large ligand like cl- will fit around the central metal atom, than of a smaller ligand like NH3. i.e (CoCL4)2- and (Co(NH3)6)3+ This in turn affects the shape of the complex ion
• Ligand charge determines the charge of a complex ion. If a ligand if neutral, the overall charge of the ligand will be positive as metal ions always have a positive charge. If the ligand is negatively charged then it is taken into account for the overall charge of the complex ion. The overall negative charge of all the ligands combined is added to the positive charge from the metal to determine the overall charge of the complex ion
• geometrical isomerism can occur when ligands differ in their position in space relative to one another. It occurs in octahedral and square planar complexes.
• optical isomerism occurs when two isomers are non-superimposable and occurs when there are two or more bidentate ligands in a complex. They are chiral, so have identical properties but can be distinguished by their effect on polarised light. One isomer will rotate the plane of polarised light clockwise, and the other anticlockwise
• transition metal complexes are coloured as they have partly filled d orbitals, so electrons can move from one d orbital to another. While in an isolated transition metal atom these d orbitals are of equal energy, in a compound the interactions with other atoms alters the energies of the d orbitals. When electrons move from one d-orbital to one of a higher energy, they absorb energy in the visible region of the spectrum equal to the difference in energy between the levels. This colour is therefore missing from the spectrum, so you see the combination of unabsorbed colours
• frequency of light is related to the energy difference in the equation: ∆E = hv where E is energy, v is frequency of light, and h is planck's constant. frequency of light is related to the colour, so the colour of a transition metal complex depends on the energy gap ∆E. The energy gap is influenced by the oxidation state of the metal, the ligands, and the shape of the complex ion. So different compounds of the same metal may have different colours
• colorimetry can be used to measure the concentration of solutions of coloured transition metal compounds. As, the more concentrated the solution, the less light can pass through, which the colorimeter reflects in its value.