Final answer:
The statement 'K3[VF] is a colourless compound' is incorrect because the color of a complex is determined by light absorption and reflection, and complexes that include transition metals like vanadium usually appear colored due to d-d transitions caused by ligand interactions.
Step-by-step explanation:
The statement "K3[VF] is a colourless compound" is not correct because the color of a complex ion is determined by the wavelength of light it absorbs, which in turn depends on the structure of the complex and its ligands. In transition metal complexes, such as those of vanadium (V), the presence of a metal ion and its ligands can lead to the absorption of certain wavelengths of light, and the compound appears as the complementary color of the absorbed light on the color wheel.
It is important to understand that we perceive the color of a substance based on the light that is transmitted or reflected, not the light that is absorbed, and that the observed color is complementary to the absorbed light. For instance, the complex [Cr(NH3)6]3+ appears yellow because it absorbs blue-violet light with its strong-field ligands. Similarly, vanadium complexes often exhibit colors due to d-d transitions where electrons in the d-orbitals absorb light energy and move to higher energy d-orbitals, and the specific ligands present in the complex influence the energy required for these transitions. Therefore, a vanadium complex like K3[VF] is likely to be colored, contradicting the notion of it being colorless.