Manganate and Permanganate

Question

In my chemistry course, the addition of the “per” prefix generally means that the oxoanion of relevance will have one more oxygen than the “base” ion.

e.g. chlorate = $\ce{ClO3-}$, perchlorate = $\ce{ClO4-}$

However, permanganate is $\ce{MnO4-}$ and manganate is $\ce{MnO4^2-}$. The charges are different but there are still four oxygen atoms in each, so it seems to violate the convention. Any thoughts?

Does this answer your question? What is the meaning of the prefix "per-"? — Nilay Ghosh, Jul 19 '22 at 01:02
It is a little unclear. It mentions “oxygenated states” but does not cover examples where the number of oxygen atoms is the same. — Ayush Tripathi, Jul 19 '22 at 01:04
Useful links for text and formula formatting: Notation basics / Formatting of math/chem expressions /
upright vs italic // Use plain texts in CH SE titles. // For more, see Math SE MathJax tutorial. — Poutnik, Jul 19 '22 at 02:32
https://chemistry.stackexchange.com/questions/59302/nomenclature-of-polyatomic-ions https://chemistry.stackexchange.com/questions/40506/what-do-the-prefixes-meta-ortho-pyro-mean-in-inorganic-chemistry — Mithoron, Jul 19 '22 at 14:37
Does this answer your question? Nomenclature of polyatomic ions — Mithoron, Jul 22 '22 at 14:35
It explains the per and other prefixes using the number of oxygen atoms, which, according to the information I have received in this question, I believe is a bit imprecise. — Ayush Tripathi, Jul 23 '22 at 15:09
A usual exercise is to take polyatomic ions of the form $\ce{MO_{x}^{y-}}$ and compute the oxidation state of $\ce{M}$. Then look at the names of these ions. — Zhe, Jul 26 '22 at 15:24

Oscar Lanzi · Accepted Answer · 2022-07-19T01:56:37.667

7

They ran out of names, maybe?

Permanganate does have more oxygen in the sense that it could formally be considered a possible product of adding oxygen to manganate:

$\ce{4MnO4^{2-} + O2 + 2H2O -> 4 MnO4^- + 4 OH^-}$

This theoretical reaction goes along with manganese having oxidation state +7 in permanganate versus only +6 in manganate. We may say that "per-" simply means higher oxidation state.

edited Jul 19 '22 at 01:56

answered Jul 19 '22 at 01:01

Oscar Lanzi

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Poutnik · Answer 2 · 2022-07-19T06:28:17.617

The general convention does not follow the number of oxygen atoms, but the order of oxidation states of the central atom.

For the increasing order of oxidation states, there are these prefixes/suffixes:

hypo- + -ite
-ite ( -ous for acids )
-ate ( -ic for acids )
per- + -ate

The naming starts with -ate (-ic), Then -ite ( -ous ) is added if there are 2 oxidation states. Which of the other two is added as the third one depends on the oxidation state of the least common one.

Manganate and Permanganate

2 Answers2