Published by:
CGP EDU Academic Team
Published on: August 13, 2026
The colour of the X 2 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 atom temperature changes from gas to solid down the group
B
decrease in HOMO-LUMO gap down the group
C
decrease in 
gap down the group
gap down the group
D
decrease in ionization energy down the group
Text Solution
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CHECK THE SOLUTION.
(b, c)
Highest occupied molecular orbital (HOMO) 
Lowest unoccupied molecular orbital (LUMO) 
On descending the group gap between 
and 
decreases
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