Which member of a family of oxanions takes the -ate ending?

I know that for naming anions, you use the ending "ate" for the common or representative oxyanion, but my question is how do you know which is the common or representative oxyanion? How do you know that CO32- is common? Or that common phosphate is PO43- not PO33-? How do you know how many O's to use?
ens106 from PSU

Sorry. There isn't any objective way to decide which formula in an oxyanion family will have an -ate ending. You'll have to memorize the names and formulas of the "-ate" ions.

What's common and what's not is the result of the peculiar chemistry of our planet. We live under an oxygen-rich atmosphere, so oxyanions in states with higher oxidation number tend to be more stable (and so more common) than those with lower oxidation number. If there were chemistry students indigenous to Io or Titan, they might memorize a different list of polyatomic ions.

A list of ions that should be learned in first semester chemistry is given in the Polyatomic Ions section.

Author: Fred Senese senese@antoine.frostburg.edu



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