# Chemistry - naming oxoanions
**URL:** https://boards.straightdope.com/t/chemistry-naming-oxoanions/611880
**Category:** Factual Questions
**Created:** [February 5, 2012, 7:04pm UTC](https://boards.straightdope.com/t/chemistry-naming-oxoanions/611880 "2012-02-05T19:04:01Z")
**Posts on this page:** 7
**Page:** 1
### Author:  [@congodwarf](https://boards.straightdope.com/u/congodwarf)
#### Post date: [February 5, 2012, 7:04pm UTC](https://boards.straightdope.com/t/chemistry-naming-oxoanions/611880/1 "2012-02-05T19:04:01Z")
I’m trying to wrap my head around naming (of everything, not just ionic compounds). I think I’m starting to get the hang of it but I need clarification on something.
When a nonmetal forms two oxoanions, the one with the larger number of O atoms has the suffix -ate and the one with fewer O atoms has the suffix -ite. When there are more than 2 oxoanions, the one with the most O atoms gets the prefix per- and the one with the fewest gets the prefix hypo-.
I get that part.
What I don’t get is - will any oxoanion always have either 1,2,3, or 4 O atoms?
Basically does:
per-xxxxxxx-ate always mean xO4
xxxxxxx-ate always mean xO3
xxxxxxx-ite always mean xO2
hypo-xxxxxx-ite always mean xO
I realize I could ask my professor this but I don’t see her again until Tuesday.
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### Author:  [@Nametag](https://boards.straightdope.com/u/Nametag)
#### Post date: [February 6, 2012, 2:00am UTC](https://boards.straightdope.com/t/chemistry-naming-oxoanions/611880/2 "2012-02-06T02:00:38Z")
No, the most common or most stable anion normally gets the -ate ending – like sulfate, SO4[2-], or carbonate, CO3[2-].
One less oxygen gets the -ite ending, and that’s usually pretty stable, too. Per\_\_\_ates are usually not that stable, and are potent oxidizers. Hypo\_\_\_ites are often reducing agents.
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### Author:  [@congodwarf](https://boards.straightdope.com/u/congodwarf)
#### Post date: [February 6, 2012, 2:33am UTC](https://boards.straightdope.com/t/chemistry-naming-oxoanions/611880/3 "2012-02-06T02:33:58Z")
Damn. In that case, is there any way (other than memorizing vast amounts of information) that I can know based on the name, what the actual anion is? I got lucky with permanganate apparently.
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### Author:  [@snailboy](https://boards.straightdope.com/u/snailboy)
#### Post date: [February 6, 2012, 9:52am UTC](https://boards.straightdope.com/t/chemistry-naming-oxoanions/611880/4 "2012-02-06T09:52:28Z")
I had to learn these in chemistry. It basically came down to memorization. I don’t think there’s any real pattern to them that you can use to avoid memorizing them individually. I just wrote a program on my computer that went through them like flashcards.
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### Author:  [@snailboy](https://boards.straightdope.com/u/snailboy)
#### Post date: [February 6, 2012, 9:55am UTC](https://boards.straightdope.com/t/chemistry-naming-oxoanions/611880/5 "2012-02-06T09:55:02Z")
By the way, manganese is a metal.
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### Author:  [@Disheavel](https://boards.straightdope.com/u/Disheavel)
#### Post date: [February 6, 2012, 9:22pm UTC](https://boards.straightdope.com/t/chemistry-naming-oxoanions/611880/6 "2012-02-06T21:22:26Z")
> [@congodwarf](#):
>
> per-xxxxxxx-ate always mean xO4
> xxxxxxx-ate always mean xO3
> xxxxxxx-ite always mean xO2
> hypo-xxxxxx-ite always mean xO
(hy)per-xxxxxxx-ate means maximum oxidated state (the core atom is maximally bound to/oxidized by oxygen)
xxxxxxx-ate always means oxidation state is one less than (hy)per
xxxxxxx-ite always means one less
hypo-xxxxxx-ite always means one less
But this gets broken for the sulfate series (which doesn’t have the persulfate)! and carbonate! and nitrate!
The reason there is no system is that the salts were all known before their exact compositions were know and as such there is much grandfathering in of their previous names. So it will be straight memorization. But you need only learn the name of the most oxidized state and build backward from there.
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### Author:  [@Carl\_Pham](https://boards.straightdope.com/u/Carl_Pham)
#### Post date: [February 6, 2012, 11:06pm UTC](https://boards.straightdope.com/t/chemistry-naming-oxoanions/611880/7 "2012-02-06T23:06:28Z")
It’s not that bad. You just have to remember this:
(1) All of the -ates have 3 or 4 oxygens. But the only -ates with 4 oxygens are Si, P, S and As, which you’ll note form a big T on the right side of the Periodic Table centered on phosphorus. Perhaps you can think of a mnemonic there, like it’s the shape of an airplane and a famous WWII airplane was the P-40 (“centered on P there are FOUR in the shape of a TEE”).
(2) One fewer O than the -ate is the -ite, two fewer is a hypo- -ite, and one more than the -ate is a per- -ate.
(3) The charges are all the same (-ate, -ite et cetera). They begin with -1 for the ion furthest to the right in the PT, which is nitrate for Period 2 (since an oxygen oxoanion makes no sense, and F can’t form more than one bond), and otherwise the halogens (chlorate, bromate, iodate).
(4) Thereafter, for each step you move left in the Table, the charge goes down by -1. Hence, chlorate (ClO3-), to the left is sulfate (SO4-2), to the left is phosphate (PO4-3), to the left one more time is silicate (SiO4-4). In Period 4 the list stops at arsenate (AsO4-3) because germanium is technically a metal, and in Period 5 the list stops at tellurate (TeO3-2) because antimony is technically a metal.