Question 1: Transition metals are known for forming coloured compounds. Explain briefly why these compounds are coloured, focusing on the role of d-orbitals and electron transitions.

Answer: Coloured compounds form because electrons in the d-orbitals absorb specific wavelengths of light when they undergo electronic transitions, promoting electrons to higher energy d-orbitals. The remaining transmitted or reflected light gives the compound its colour.

Question 2: Define the term 'coordination complex' in the context of transition metal chemistry.

Answer: A coordination complex is a compound formed when a transition metal ion bonds to one or more ligands through coordinate covalent bonds.

Question 3: Which part of the electromagnetic spectrum do transition metal complexes typically absorb to appear coloured?

Answer: They typically absorb light in the visible region of the electromagnetic spectrum.

Question 4: Explain how the oxidation state of a transition metal influences the colour of its compounds.

Answer: The oxidation state affects the number of d-electrons and the energy gap between d-orbitals, which influences the wavelength of light absorbed and thus the observed colour.

Question 5: Calculate the energy (in joules) of a photon of light with a wavelength of 500 nm, which could be absorbed by a transition metal complex.

Answer: Using E = hc/λ, where h=6.626 × 10⁻³⁴ Js, c=3.00 × 10⁸ m/s, and λ=500 nm (5.00 × 10⁻⁷ m), E = (6.626 × 10⁻³⁴)(3.00 × 10⁸)/(5.00 × 10⁻⁷) = 3.97 × 10⁻¹⁹ Joules.

Question 6: Identify the variables that can affect the colour intensity of a transition metal complex in a solution.

Answer: Variables include the concentration of the complex, the nature of the ligands, the oxidation state of the metal, and the pH of the solution.

Question 7: Describe a simple experiment to observe the colour change when a transition metal complex reacts with a ligand.

Answer: Prepare a solution of a transition metal salt (e.g., copper sulfate). Add a ligand such as ammonia solution gradually. Observe the colour change from blue to a deeper blue or green as the complex forms. Explain that the ligand alters the d-electron environment, changing the absorption spectrum.

Question 8: Multiple choice: Which of the following ligands typically produce a strong colour in their complexes?

Answer: All of the above

Question 9: Fill in the blank: The colour of a transition metal complex is primarily due to the absorption of specific wavelengths of __________ of light.

Answer: visible

Question 10: Explain how the crystal field theory accounts for the colours observed in transition metal complexes.

Answer: Crystal field theory describes how ligands create an electric field that splits the degenerate d-orbitals into different energy levels. The energy difference corresponds to certain wavelengths of visible light. When electrons transition between these split d-orbitals, specific wavelengths are absorbed, and the remaining light gives the compound its characteristic colour.