Writing and Naming a Compound with Polyatomic Ions?

Could you describe in detail how to write the name and compound produced by combining ions. For example, what does NH4 1+ and CO3 2+ equal together? And Au 3+ and SO4 2-?


Could you explain to me how you came to those answers. I am in grade 9 , so please make sure that your explanation is at my level.

Writing and Naming a Compound with Polyatomic Ions?
When you name compounds, you switch the charges to form subscripts.








So, for NH4 1+ and CO3 2-....


Since NH4 has a +1 charge, CO3 is going to have a subscript of 1. Since CO3 has a -2 charge, NH4 is going to have a subscript of 2.





Therefore, the formula would be:


==%26gt; (NH4)2CO3











You do the same process for Au 3+ and SO4 2-. Since Au has a +3 charge, SO4 is going to have a subscript of 3. Since SO4 has a -2 charge, Au is going to have a subscript of 2.





Therefore, the formula would be:


==%26gt; Au2(SO4)3














I hope this helps! :)
Reply:When you write the formulas, you have to make sure that all the charges balance (which means you have to be very careful to write the charges!)





Since NH4 has a +1 charge and the CO3 has a MINUS two charge, you need twice as many NH4's as CO3's. Since the NH4's have more than one atom, you have to use ( )'s. So the formula is: (NH4)2CO3. For the name, just say the names of the ions: Ammonium carbonate





The second formula is done in a similar fashion. It is Au2(SO4)3. Note that ( )'s are not needed for the Au. The naming is a little different. Since Au has two possible charges, you have to specify the charge by writing Roman numerals. Its name is gold(III) sulfate. (That's the US. It's gold(III) sulphate in most of the rest of the world.)
Reply:(In your question, the CO3 is 2- not 2+)


.


Here, we 'Cross-over' the Valence of each ion to form the compound. The NH4 group valence = 1 and CO3 group = 2.


'Cross over' the 1 and the 2 giving...


2 x NH4(1+) and 1 x CO3(2-) ===%26gt; (NH4)2CO3 (Electrically neutral)





Au can have a valence of 1 or 3. As Au(1+) or Au(3+)





a)..Au(1+) + SO4(2-) will become 2 x Au(1+) + 1 x SO4(2-) = Au2SO4.





b)..Au(3+) + SO4(2-) needs some adjustment as follows.


In order to become neutral, we will need 2 x Au(3+) + 3 x SO4(2-) to give Au(6+) and SO4(6-) = Au2(SO4)3.