What is the color of chromium Cr##^{3+}##?

[chwala]

kindly clarify on the color of chromium $cr^{3+}$. Is it green or grey-green? There is a conflict in my textbook i.e Roger Norris IGCSE Chemistry and the cie syllabus content 2019. regards,

 

[DrClaude]

You'll find some pictures here: http://www.public.asu.edu/~jpbirk/qual/qualanal/chromium.html

 

[Borek]

No such thing as $cr^{3+}$, you mean $Cr^{3+}$.

Naming colors is never easy. First, they can be perceived differently by different people (remember the discussion about whether the dress on a picture picture was colored black and blue, or white and gold?). Second, we have names for some basic colors, but when it comes to different hues we are often at loss with naming. So actually the discussion about whether Cr³⁺ is green or grey-green is a bit of a moot - it is what it is, and neither name is precise enough.

 

[symbolipoint]

We do not know what color we see. Use spectrophotometers.

 

[Klystron]

While the above answers to your question "What is the color of Chromium III ?" are correct and responsive, I can add a perspective from the chemical nature of fine art. Depending on how it is prepared and how long the sample is exposed to atmosphere expect a sample to appear 'light green' to 'grayish green' in visible light. Note the sample in post #2 may be subject to both oxidation and nitrification with resulting 'color change' as we learn in this excerpt Chemistry and compounds.

 

[sigoldberg1]

Ans: Looks like both, depending for Cr2O3. See https://www.google.com/search?biw=1292&bih=695&tbm=isch&sa=1&ei=KzfOXK-7I8Xm_Qbbq5HQAw&q=cr2o3&oq=cr2o3&gs_l=img.3..0l10.27306.31418..34591...0.0..0.96.393.5......1....1..gws-wiz-img.......35i39j0i67.EPzWGoCfhk4 .

 

[symbolipoint]

I must have seen solutions of Cr⁺³ a couple of times and best that I remember, green; much like the color shown in post # 6, the picture on the left side.

 

[TeethWhitener]

Anhydrous chromium (III) chloride is purple. The color depends on the ligand field in addition to the metal center.

 

[pinball1970]

Ans: Looks like both, depending for Cr2O3. See https://www.google.com/search?biw=1292&bih=695&tbm=isch&sa=1&ei=KzfOXK-7I8Xm_Qbbq5HQAw&q=cr2o3&oq=cr2o3&gs_l=img.3..0l10.27306.31418..34591...0.0..0.96.393.5......1....1..gws-wiz-img.......35i39j0i67.EPzWGoCfhk4 .
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The problem with images from different sources on one screen can result in the same colour looking different. I think 'green' is good enough