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JEE Advanced 2017Paper 1
Exam
JEE Advanced
Year
2017
Paper
Paper 1
Subject
Chemistry
Chapter
Classification of Elements and Periodicity in Properties

JEE Advanced 2017 · Paper 1 · Chemistry · Classification of Elements and Periodicity in Properties

The colour of the X _ 2 molecules of group 17 elements changes...

The colour of the X2{X}_{2} molecules of group 17 elements changes gradually from yellow to violet down the group. This is due to -The colour of the X _ 2 molecules of group 17 elements changes gradually from yellow to violet down the group. This is

Options

  1. ADecrease inHOMO−LUMOinHOMO - LUMO gap down the group
  2. BDecrease in π∗−σ∗{\pi}^{*} - {\sigma}^{*} down the group
  3. CThe physical state of X2{X}_{2} at room temperature changes from gas to solid down the group
  4. DDecrease in ionization energy down the group

Correct answer

A. Decrease inHOMO−LUMOinHOMO - LUMO gap down the group

Step-by-step solution

Halogens are coloured due to HOMO-LUMO transition of electrons.

The colour of the X _ 2 molecules of group 17 elements changes gradually from yellow to violet down the group. This is

On moving down the group HOMO-LUMO energy gap decreases so transition of electrons become easier from  Π∗2px{{Π}^{*}}_{2{p}_{x}} to σ∗2pz{{\sigma}^{*}}_{2{p}_{z}} therefore colour intensify.

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