posted by Nelle .
I have a compound of Na2subscriptCO3subscript. The cation it breaks into is NA+1 in the upper righthand corner, and the anion is CO3subscript,-2in the upper right hand corner. Where did the anion numbers come from? How can you tell what the charge is? I know you either look in the periodic table square, or at the top of the periodic column, but I don't see where the charge of -2 comes from since carbon is in the +4 column. Thanks for clarifying this.
Na has a +1 charge because its in the first group of the periodic table. For the CO3, didn't the teacher give you a sheet of common ions that tells you what the charges are? That was what my teacher did. But if you don't have the sheet, I THINK the reason why it has a -2 charge is because of the oxygen. If do not do anything with the C.
Chopsticks is right. Usually you memorize a set of common anions. Here is a link to a set that includes more than just the common ones.
(Broken Link Removed)
But in your case, it is far easier to do it another way. Sodium carbonate is Na2CO3. You know Na is +1 and two of them make a total of +2 on the Na. Since every compound is neutral, you KNOW the remainder is -2 (the carbonate or CO3). If you wanted to determine C, you could do that also. Na is +1, that makes a total of +2. Oxygen is -2 which makes a total of -6 for three of them. Now, what must C be to make zer?. It must be +4.