Chromium(II) oxide explained

Chromium(II) oxide (CrO) is an inorganic compound composed of chromium and oxygen. It is a black powder that crystallises in the rock salt structure.^[1] Hypophosphites may reduce chromium(III) oxide to chromium(II) oxide:

H₃PO₂ + 2 Cr₂O₃ → 4 CrO + H₃PO₄

It is readily oxidized by the atmosphere. CrO is basic, while is acidic, and is amphoteric.^[2]

CrO occurs in the spectra of luminous red novae, which occur when two stars collide. It is not known why red novae are the only objects that feature this molecule; one possible explanation is an as-yet-unknown nucleosynthesis process.^[3]

See also

• Chromium(IV) oxide
• Chromium(VI) oxide

Notes and References

1. Egon Wiberg, Arnold Frederick Holleman (2001) Inorganic Chemistry, Elsevier
2. Chemistry 7th edition, by Raymond Chang page 645 (problem 15.100)
3. 2015A&A...580A..34K. 1504.03421. Post-outburst spectra of a stellar-merger remnant of V1309 Scorpii: From a twin of V838 Monocerotis to a clone of V4332 Sagittarii. Astronomy & Astrophysics. 580. A34. Kamiński. T.. Mason. E.. Tylenda. R.. Schmidt. M. R.. 2015. 10.1051/0004-6361/201526212. 118566357.