Question

The colour of the X₂ molecules of group 17 elements changes gradually from yellow to violet down the group. This is due to(A) The physical state of X₂ at room temperature changes from gas to solid down the group(B) Decrease in ionization energy down the group(C) Decrease in π* - σ* gap down the group(D) Decrease in HOMO-LUMO gap down the group

Answer 1

The colour of X2 molecules of halogens is due to absorption of light in the visible region. The energy acquired in this manner excites the valence electron from the highest occupied molecular orbital (HOMO) to the lowest unoccupied molecular orbital (LUMO),

Option C and D  are correct