Unit 2: Section 4 - Transition Metals
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Define a transition element
An element which forms at least one stable ion with a partially full d-shell of electrons
What are some physical properties of transition metals?
• Metallic • Good conductors of heat and electricity • Hard • Strong • Shiny • High m.p • High b.p • Low reactivity
What are some uses of iron?
Vehicle bodies, to reinforce concrete
What are some uses of titanium?
Jet engine parts
What are some uses of copper?
Water pipes
What are the characteristic chemical properties of transition metals (4)?
• Variable oxidation states -> take part in many redox reactions • Coloured compounds/ions in solution • Good catalysts • Form complex ions
Define the term complex ion
Central transition metal ion surrounded by ligands (other ions/molecules) that are co-ordinately bonded to it
Give some examples of transition metals catalysts amd the processes/reactions they catalyse? (3)
Iron - Haber process Vanadium (V) oxide - contact process MnO2 - decomposition of H2O2
Which electrons do transition metals lose first when forming ions?
4s
Define the term ligand
An ion or molecule with at least one lone pair of electrons, that donates them to a transition metal ion to form a co-ordinate bond and thus a complex ion
Define the term mono/unidentate ligands
A ligand that forms one co-ordinate bond to the central metal ion (one lone pair to donate)
Define the term bidentate ligand
A ligand that forms two co-ordinate bonds to the central metal ion (2 lone pairs to donate)
Define the term multidentate ligand
A ligand that forms three or more co-ordinate bonds to the central metal ion
Give some examples of common monodentate ligands (4)
Cl- H2O NH3 CN-
How many co-ordinate bonds does EDTA4- form?
6
Define the term coordination number?
The number of co-ordinate bonds the metal ion has formed to surrounding ligands
What is the chelate effect?
Chelate complexes with multidentate ligands are favoured over monodentate ligans or ligands that form fewer co-ordinate bonds per molecule
Explain the chelate effect in terms of entropy and the reaction that is occurring
• Number of molecules increases when multidentate ligands, e.g. EDTA, displace ligands that form fewer co-ordinate bonds per molecule • Significant increase in entropy -> Gibbs’ free energy change , 0 -> feasible reaction • A more stable complex ion is formed
What ion is usually formed when a transition metal compound is dissolved in water? What shape is it?
Aqua ion 6 H2O ligands around the central metal ion. Octahedral complex is formed
If a transition metal ion has 2 ligands, what shape is it usually?
Linear
If a transition metal ion has 4 ligands, what shape is it usually?
Tetrahedral
Name an exception to the general rule that ions with 4 ligands is generally tetrahedral. What shape is it?
Platin is square planar -> forms cisplatin
What shape is a complex ion if it has 6 ligands?
Octahedral
How can complex ions display E-Z or cis-trans isomerism? What shapes of ion does this apply to?
• Ligands differ in the way in which they are arranged in space • 2 ligands of the same type can be on the same side of the metal ion (next to each other), which forms the Z or cis isomer • 2 ligands of the same type can be on opposite sides of the metal ion (not next to each other), which forms the E or trans isomer • Applies to square planar and octahedral complex ions