According to Wikipedia,

[...] It is a colorless solid that readily sublimes into intensely yellow vapors.

It is clear from the above statement that $\ce{XeF6}$ is colourless in solid form. But why should it be coloured when it converts into vapour form?

  • $\begingroup$ Bottom line is it depolymerises. $\endgroup$
    – Mithoron
    Commented Sep 9, 2022 at 18:27
  • $\begingroup$ There is nothing unusual about vapors of elements/compounds appearing colored. It is a common phenomenon. Potassium is a silvery white metal but its vapors appear green! Sodium also shows colored vapor. People have spent their trying to understand the structure of xenon hexafluoride. $\endgroup$
    – AChem
    Commented Sep 9, 2022 at 23:49
  • $\begingroup$ Related for oxygen: chemistry.stackexchange.com/questions/15035/… Oxygen is colorless at gaseous state but is slightly colored in liquid and solid state. $\endgroup$ Commented Sep 10, 2022 at 4:08
  • 1
    $\begingroup$ @NilayGhosh, This oxygen issue is perhaps a different phenomenon. It is simply a concentration effect (Beer's law). Just like heavy water appear blue when viewed in a very long path length tube but in an ordinary beaker it is colorless pure white liquid. Xenon hexafluoride is complicated in the sense that there must be a change in the nature of bonding in the solid phase and gas phase. Just like potassium and sodium vapor. One would never assume that potassium has a beautiful green vapor. $\endgroup$
    – AChem
    Commented Sep 10, 2022 at 15:59


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