1. A ligand acts as what in coordinate bonding?
- Proton donor always
- Electron-pair acceptor only
- Electron-pair donor
Check the answer and reasoning
Electron-pair donor
Its lone pair forms a coordinate bond to the metal centre.
CHEM / A2 level
Transition elements and inorganic trends
Transition-element chemistry includes variable oxidation states, coloured complexes and catalytic behaviour. Ligands donate electron pairs to metal centres; coordination number counts donor atoms attached.
Learning objectives
- Explain transition elements and inorganic trends using a concrete example.
- Apply the worked method and justify each step.
- Recognise the limitation described in the final check.
The big idea
Transition-element chemistry includes variable oxidation states, coloured complexes and catalytic behaviour. Ligands donate electron pairs to metal centres; coordination number counts donor atoms attached.
Ligand exchange can change colour and stability. Compare Group 2 and halogen trends through charge density, bond energies and hydration rather than applying a single trend to every property.
Worked example
Six monodentate ligands bind one metal ion. What is its coordination number?
Follow the solution
Each ligand contributes one donor atom, so six donor atoms coordinate the metal.
Investigate and explain
Predict the worked result before calculating. Change one input, record the new result, and explain which assumptions still hold.
Use the evidence activity below; no exact PhET model is claimed.
Check your understanding
2. Six monodentate ligands bind one metal ion. What is its coordination number?
- 6
- 3
- 12
Check the answer and reasoning
6
Each ligand contributes one donor atom, so six donor atoms coordinate the metal.
3. Does every coloured solution necessarily contain a transition metal?
- Yes
- No
- Only if blue
Check the answer and reasoning
No
Colour can arise from many electronic structures; it is evidence to interpret, not a unique identification.