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Chemistry Forums for Students => High School Chemistry Forum => Topic started by: michaelscwu on June 22, 2009, 08:17:42 AM

Title: Why permanganate has a different charge and same # of O as manganate?
Post by: michaelscwu on June 22, 2009, 08:17:42 AM
As a general rule, when a polyatomic ion's prefix or suffix changes it just means that the ion either has more or less oxygen but retains the charge.
i.e. carbonATE CO3 (2-) and carbonITE CO2 (2-)

How come manganate, MnO4 (2-), has the same number of oxygen as PERmanganate, MnO4 (1-), and has a different charge?

Shouldn't PERmanganate have 1 more oxygen than manganate, and shouldn't the two have the same charges?
Title: Re: Why permanganate has a different charge and same # of O as manganate?
Post by: Borek on June 22, 2009, 08:44:27 AM
Quote from: michaelscwu on June 22, 2009, 08:17:42 AM
Shouldn't PERmanganate have 1 more oxygen than manganate, and shouldn't the two have the same charges?

Well, mother nature doesn't follow our general rules, quite the opposite - our general rules try to follow mother nature. The don't always succeed.
Title: Re: Why permanganate has a different charge and same # of O as manganate?
Post by: michaelscwu on June 22, 2009, 09:00:56 AM
Quote from: Borek on June 22, 2009, 08:44:27 AM
Quote from: michaelscwu on June 22, 2009, 08:17:42 AM
Shouldn't PERmanganate have 1 more oxygen than manganate, and shouldn't the two have the same charges?

Well, mother nature doesn't follow our general rules, quite the opposite - our general rules try to follow mother nature. The don't always succeed.

Is there a reason why though? Are they two completely different things?
Title: Re: Why permanganate has a different charge and same # of O as manganate?
Post by: Borek on June 22, 2009, 09:13:12 AM
Not sure what you are asking about this time.

Manganate and permanganate are two different things. They differ by one electron.

Cr2+ and Cr3+ are two different things. They differ by one electron.

Fe(CN)63- and Fe(CN)64- are two different things. They differ by one electron.
Title: Re: Why permanganate has a different charge and same # of O as manganate?
Post by: lancenti on June 22, 2009, 09:57:10 PM
I think that the prefix of PER such as that found in Perchlorate and Permanganate simply mean that it's one oxidation state higher and not that there should be one more oxygen atom attached.

EDIT:

I think that the reason we have this idea comes from how PERoxide = 2 oxygen atoms.