CO3, known as the carbonate ion, carries a negative charge of 2. This means that CO32- is the correct notation for the ion.
The reason behind this charge is due to the structure of the carbonate ion itself. It is composed of one carbon atom centrally located and surrounded by three oxygen atoms. The carbon atom forms single bonds with two oxygen atoms and a double bond with the third oxygen atom. In this arrangement, the two single-bonded oxygen atoms each contribute a -1 charge, while the double-bonded oxygen does not add any additional charge. Thus, the total negative charge sums to -2.
This configuration is crucial for understanding how carbonate interacts with other ions and molecules. For instance, when carbonate ions combine with metal ions, they often form salts. Knowing the charge of the carbonate ion helps in predicting the ratio of carbonate to metal ions needed to form neutral compounds.