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AS OCR A Chemistry: How to write the formula of ionic compounds with roman numerals Watch

1. Hey guys can you explain how to solve this problem? Many thanks.

Q. Write the formula of the sulfate(IV)ion and the chlorate(III)ion
A. SO3^2- and ClO2^-
2. (Original post by thecutiemarshy)
Hey guys can you explain how to solve this problem? Many thanks.

Q. Write the formula of the sulfate(IV)ion and the chlorate(III)ion
A. SO3^2- and ClO2^-
The roman numeral stands for the charge on the positive ion in a compound.

The sulphate (ALWAYS) contains 1 sulphur bonded with 3 oxygens and you are given that the sulphur has a charge of 4+ by the roman numeral, therefore the overall ion must be 2- because the charge on an oxygen ion is always 2- and there are 3 of them. (3x - 2 = -6, -6+4 = -2)

ClO2^-

You are given that the chlorine ion has a charge of +3 by the numeral.
Oxygen always has a charge of -2
So you have -4+3 overall giving -1

Just tag me if you don't understand still
3. Hey thank you for your response!
I understand the first question, but for the second, how is chlorine bonded with 2 oxygen atoms?
Wouldn't it be Cl2O as Cl has -1 charge whilst O has -2 charge.
Sorry we hadn't really covered this in class :s
4. (Original post by thecutiemarshy)
Hey thank you for your response!
I understand the first question, but for the second, how is chlorine bonded with 2 oxygen atoms?
Wouldn't it be Cl2O as Cl has -1 charge whilst O has -2 charge.
Sorry we hadn't really covered this in class :s
Oxygen is always -2 unless in peroxides. If it is chlorate (III) then the oxidation state of chlorine is +3, thus it can be deduced that as an anion, its overall charge must be -1.
5. (Original post by AnIndianGuy)
Oxygen is always -2 unless in peroxides. If it is chlorate (III) then the oxidation state of chlorine is +3, thus it can be deduced that as an anion, its overall charge must be -1.
Hi, I am aware of the oxidation rules but its not addressing the part I dont understand.

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