Oxidation States: A Closer Look at 2+ and +2

[RichRobX]

When writing oxidation states, is there a difference between 2+ and +2?

 

[Gokul43201]

I believe convention requires that you use +n or -n to represent oxidation states, and m+ or m- to denote the net chrge on some species.

Example : In the radical $SO_4^{~2-}$, the oxidation state of S is $+6$.

 

[movies]

You often see the oxidation state written in Roman numerals, so S^VI in Gokul's example.

 

[dextercioby]

Even with Roman numerals,u still need the sign.Dor example Sulphur:$$S^{II}$$ is it for a metalic compound or for a nonmetalic compound...?

Daniel.

 

[movies]

Even with Roman numerals,u still need the sign.Dor example Sulphur:$$S^{II}$$ is it for a metalic compound or for a nonmetalic compound...?

Daniel.

True! I should have written S^+VI.

Often times I think that the '+' is assumed unless you use a '-'

 

[dextercioby]

The distinction needs to be done each time an nonmetalic compound experinces more than one ON,and of opposite signs.
So u may use the Roman Numerals at free will,just along you assure yourself that your notation will not raise confusions among the readers...

Daniel.

 

[Gokul43201]

I have never come across the notation, $Fe^{+II}$ , for example. I've usually seen Roman Numerals designate oxidation states in complexes, but then the oxidation state appears in brackets, not as a superscript.

Ex : dichlorotetramminecobalt(III) chloride

 

[The Bob]

I have never come across the notation, $Fe^{+II}$ , for example. I've usually seen Roman Numerals designate oxidation states in complexes, but then the oxidation state appears in brackets, not as a superscript.

Ex : dichlorotetramminecobalt(III) chloride

I must say that I have never come across Roman Numerials in formulae either. Is there an reason to use one instead of the other or are they interchangeable?

The Bob (2004 ©)

 

[chem_tr]

I remember that the notation 2+ is preferred over +2, since it can be mixed up with exponential expressions, I mean, when we write [SO₄^-2]^-2, it may confuse somebody, which one is the electronic charge and which one is a mathematical expression? So to distinguish them, charges are written in the form n+ or n-. In my TA years, I explained the issue to the pupils like that and tried to get them used to writing like this. I hope I was not wrong.

 

[movies]

I like chem_tr's explanation. It seems to make the most sense to me.

Maybe the Roman numerals thing I mentioned before is outdated, or at least isn't as common as I thought it was. I'm not even sure where I learned it, but it seems like I see it fairly regularly. It's definitely something that is more associated with metals than organic molecules, probably because metals have more interesting oxidation states. I guess I always assumed that it was to denote the oxidation state of the metal without confusing it for a formal charge (as in a net neutral organometallic complex like ferrocene, which contains Fe²⁺).