Answer: Number of unpaired electrons (and thus high-spin vs low-spin configuration).
- A Number of unpaired electrons (and thus high-spin vs low-spin configuration)
- B The exact charge carried by each coordinated ligand
- C The metal's oxidation state read off directly without any calculation
- D The precise colour the complex will display in solution
Correct answer: A. Number of unpaired electrons (and thus high-spin vs low-spin configuration)
Explanation: By measuring the magnetic moment and using mu = sqrt(n(n+2)), we can determine n (unpaired electrons), which reveals the spin state and d electron configuration.
Aqueous solutions of transition metal ions show characteristic colours caused by electrons absorbing visible light to jump between split d-orbitals; the exact colour depends on the metal, its oxidation state, and surrounding ligands.
Concept context
Transition metals (d-block) and lanthanides/actinides (f-block). Known for coloured compounds, variable oxidation states, complex formation, and catalytic properties. Frequently tested in JEE and NEET.