AgCl and NaCl are colourless. NaBr and NaI are colourless but AgBr and AgI are coloured. This is because:

• a.) Ag⁺ polarises Br⁻ and I⁻
• b.) Ag⁺ has unpaired d – orbital.
• c.) Ag⁺ depolarises Br⁻ and I⁻
• d.) None of the above is correct

The color differences between these compounds can be attributed to the nature of the silver ion (Ag⁺) and its interactions with the halide ions. In the case of AgBr and AgI, the silver ion has a strong ability to polarize the electron clouds of the bromide (Br⁻) and iodide (I⁻) ions. This polarization leads to the formation of color due to the presence of unpaired electrons in the d-orbitals of Ag⁺, which can absorb visible light. Therefore, the correct answer is:

Correct Answer

a.) Ag⁺ polarises Br⁻ and I⁻

Why This Happens

• Ag⁺ has a high charge density, allowing it to distort the electron cloud of the halide ions.
• This distortion results in electronic transitions that can absorb light, leading to color.

In contrast, NaCl, NaBr, and NaI do not exhibit this behavior, as their ionic bonds do not involve significant polarization, keeping them colorless.