This is an ionic compound. Chromium is a transition metal cation and CO${_3}$ is an anion with a charge of 2-, as said in my chemistry textbook.

And since CO${_3}$ has a charge of 2-, the over all charge of CO${_3}$ would be 6-, since it has a subscript of 3 in the bolded formula above. So my guess is that since Chromium has no such subscript, its charge would automatically be 6-, which should be right because it would cancel out both charges.

Therefore it would be Chromium (VI) Carbonate? Please correct me if I am wrong.

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    $\begingroup$ Fairly sure this thing doesn't exist to begin with - it would immediately decompose to $\ce{CrO3 + 3CO2}$. $\endgroup$ – orthocresol Nov 28 '16 at 23:10
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    $\begingroup$ Scifinder agrees with @ortho. The only compound with the molecular formula $\ce{C3CrO9}$ to be found is tricarbonatochromate(III). $\endgroup$ – Jan Nov 28 '16 at 23:40
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    $\begingroup$ I'm quite sure you have a typo there and if it's not supposed to be 'am I right" question, you should take this to mind - it may be CrCO3 but not this. even if compound with your formula existed it wouldn't be ionic, but covalent. $\endgroup$ – Mithoron Nov 28 '16 at 23:56
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    $\begingroup$ Honestly I think even the Cr(III) compound $\ce{Cr2(CO3)3}$ doesn't exist. The aluminium and iron(III) carbonates certainly don't. With that said I'd presume this is just a nomenclature exercise and the question setter just didn't bother thinking twice about whether the compound was realistic or not. $\endgroup$ – orthocresol Nov 29 '16 at 0:05
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    $\begingroup$ @orthocresol Well, at least chromium(III) carbonate seems to exist. $\endgroup$ – Jan Nov 29 '16 at 14:25

You are pretty close. The chromium will have a 6+ charge (not 6-). I suspect this may have been a typo, because you are right in understanding the need to cancel out charges to generate an overall neutral molecule.

The only other correction is that there is no need to capitalise. So, the correct name is chromium(VI) carbonate.

  • $\begingroup$ The correct name, if it existed. $\endgroup$ – matt_black Nov 29 '16 at 15:07
  • $\begingroup$ Actually, the correct name, regardless of whether it exists or not. Even hypothetical chemical compounds need to have correct names. Nothing in this question asked about validity of the compound. Nitrogen pentafluoride needs a name whether it exists or not. $\endgroup$ – long Nov 29 '16 at 20:20

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