Question

Explain giving reasons why the halogens are coloured and the colour deepens from fluorine to iodine.

Explain why:

Halogens are coloured and the colour deepens on moving down in the group from fluorine to iqdine.

Answer 1

1. Halogens are coloured because their molecules absorb light in the visible region, exciting outer electrons to higher energy levels.
2. The atomic size increases from fluorine to iodine, causing the excitation energy to decrease down the group.
3. Fluorine absorbs high-energy violet light (appears pale yellow), while iodine absorbs lower-energy yellow-green light (appears violet).
4. This causes the colour to deepen from pale fluorine to dark violet iodine.

Answer 2

This is because halogen molecules (X₂) absorb light in the visible region and transmit complementary colors. This is because moving from fluorine to iodine, ionization enthalpy decreases.