Understanding Naming Ionic Formulas: Parentheses and Roman Numerals Explained

[Tabe]

Okay, I am so confused about how to determine whether or not you have to use the parenthesis with the Roman numeral. It is confusing me because some of the compounds that I have to write the name for, are ternary compounds, and I'm not sure which order they go in.

 

[Gokul43201]

Give us an example showing where your confusion lies, and we'll help you out with it.

 

[Tabe]

The problems that I was having trouble with are: CuC2H3O2 and CaC2O4
*the numbers are subscripts by the way*
for the first one I got Copper carbon hydrogen peroxide
for the second one I got Calcium oxalate.
Also, I'm not sure if I did this problem right: Hg2Cl2
For the answer, I got Copper (II) Sulfate. Is that right, or have I been doing this completely wrong?

 

[Gokul43201]

The problems that I was having trouble with are: CuC2H3O2 and CaC2O4
*the numbers are subscripts by the way*
for the first one I got Copper carbon hydrogen peroxide
for the second one I got Calcium oxalate.
Also, I'm not sure if I did this problem right: Hg2Cl2
For the answer, I got Copper (II) Sulfate. Is that right, or have I been doing this completely wrong?

The first is actually copper acetate, or Cu(+) CH3COO(-). It is important that you recognize that this has an organic radical. Hydrogen peroxide (H2O2) is a compound (albeit a little unstable - but then, most peroxide linkages are unstable) by itself, and I surely have never heard of it existing as such, as part of another compound.
The second is correct.

As for the third, I'm sure you've mistyped something, because Hg2Cl2 is definitely not copper sulfate !

I'll leave this to chem_tr : he's the resident expert in organometallics, and your particular type of problem is rather unusual. Further, it's not clear what level you are at.

 

[Tabe]

Well, for the third problem, I kinda typed the question on the opposite page. The correct problem should have been Hg2Cl2, which I think would be Mercury (I) chloride.

 

[Gokul43201]

That's right.