Why is solid sodium chloride white - and for that matter, why are the majority of salts white in solid form?

  • $\begingroup$ Possible duplicate of Why is snow white? $\endgroup$
    – Mithoron
    Jan 15, 2017 at 17:39
  • $\begingroup$ chemistry.stackexchange.com/questions/42303/… $\endgroup$
    – Mithoron
    Jan 15, 2017 at 17:43
  • 2
    $\begingroup$ I'll point out that in mineralogy a streak test (geology.com/minerals/streak-test.shtml) is used to help identify the mineral. The gist is that the color of the fine particles created by rubbing the mineral across a plate of alumina is observed. For any mineral of light color the streak will probably be white or whitish, but for very dark colored minerals a very different color can often be observed. $\endgroup$
    – MaxW
    Jan 15, 2017 at 17:55
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    $\begingroup$ Possible duplicate of why are simple organic molecules usually white? $\endgroup$
    – Jan
    Jan 15, 2017 at 20:29
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    $\begingroup$ Considering that sodium chloride is neither snow nor a simple organic molecule, I'm not sure how much of a duplicate this is. The argument has already been had in the comments on the latter question. $\endgroup$ Jan 15, 2017 at 21:52

1 Answer 1

  1. Sodium chloride is colorless because the electrons are tightly bond tho the sodium cation and the chloride anion. Visible light has not enough energy to excite the electrons to higher energy levels. So there's no absorption or emission of visible light of a certain wavelength and therefore no color.

  2. I wouldn't say that the majority of salts is colorless, since the more complex the composition of a salt is the more likely it is not colorless.

  • $\begingroup$ "Majority" is perhaps the wrong word, but practically all oxides, (pseudo-)halides, sulfates, nitrates etc. of main group metals are white, plus great many more. The big exception are compounds containing late transition metals, being often coloured. $\endgroup$
    – Karl
    Jan 15, 2017 at 20:53

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