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Discussion Forum



1)

The color of the X2 molecules of group 17 elements changes gradually from yellow to violet down the group. This is due to


A) decrease in π∗−σ∗ gap down the group

B) decrease in ionisation energy down the group

C) the physical state of X2 at room temperature changes from gas to solid down the group

D) decreases in HOMO-LUMO gap down the group

Answer:

Option A,D

Explanation:

Color of halogen arises due to the transition from HOMO to LUMO   in the visible regions. On moving down a group, the difference in energy between HOMO  and LUMO decreases electronic transition occurs more easily and color intensity increases.