Transition Metals
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Define what is meant by a transition element.
a d-block element that can form at least one stable ion with a partially filled d subshell
State and explain the two exceptions when deducing electron configurations.
• copper and chromium • adjusted to make the d-orbital fully filled or half filled
Explain why zinc and scandium are not considered transition metals.
• scandium only forms a 3+ ion which has an empty d subshell • zinc 2+ ions have a full d subshell
State what is meant by a complex ion
a central transition metal ion surrounded by ligands bonded by co-ordinate bonds
State what is meant by a ligand.
an ion/molecule that has at least one lone pair of electrons and forms a dative bond with a transition metal ion
State the shapes of the molecules with co-ordination number: - 6 - 4 - 2
6 → octahedral 4 → tetrahedral (or square planar) 2 → linear
Describe the structure of haem.
→ multidentate ligand → consists of 4 groups → bonded to Fe ion through co-ordinate bonds
State what is meant by a bidentate ligand.
a ligand that has two lone pairs (from two different atoms)
how many bonds does EDTA⁴⁻ form?
6
Give two examples of a bidentate ligand.
→ ethanedioate → ethane-1,2-diamine
State which complexes show optical isomerism.
octahedral complexes with bidentate ligands
State which complexes show cis-trans isomerism
• octahedral complex that has: → 4 ligands of same type → two ligands of another type • square planar complexes
Explain what is meant by the chelate effect.
→ monodentate ligands are replaced by multidentate ones → this increases entropy (more moles on products side) → higher entropy = more -ive ΔG meaning reaction is more feasible
State the equation relating energy and frequency.
ΔE = hf
What is the effect of increasing ΔE on frequency absorbed?
large ΔE = higher frequency absorbed ( therefore lower frequency observed)
State the three factors that affect the frequency absorbed.
• oxidation state • ligand type • co-ordination number
Order the ligands from low to high frequency absorption.
Cl⁻ F⁻ OH⁻ H₂O NH₃ CN⁻
Which colours are observed if a high frequency is absorbed?
low frequency colours
colour wheel
→ pink + green → red + cyan → purple/blue + yellow
What is colorimetry used for?
used to measure the concentrations of transition metal ions in solution.