What is the charge of oxalate (C2O4)?

The charge of the oxalate ion (C2O4) is indeed -2. This determination arises from the overall structure and charge distribution within the ion.

Oxalate is a simple anion composed of two carbon atoms and four oxygen atoms. In this ion, the oxygen atoms are typically assigned a charge of -2 each. Since there are four oxygen atoms, the total contribution to the charge from the oxygen is -8. Each carbon atom can be thought of as contributing to the overall stability of this charge distribution. To balance this -8 charge and give the entire ion a stable structure, the two carbon atoms contribute a +6 charge (each carbon has a +3 oxidation state in this case). When we sum these charges, the -8 from the oxygen and the +6 from the two carbons results in an overall charge of -2 for the oxalate ion.

This -2 charge is significant because it determines how the oxalate ion interacts in various chemical reactions and its role in forming salts with positively charged ions. Understanding the charge of such ions is crucial for predicting reaction outcomes and stability in chemical compounds and solutions.