The oxidation number of CO3 is -2. This is because oxygen typically has an oxidation number of -2, and there are three oxygen atoms in CO3. Since the overall charge of the carbonate ion is -2, the oxidation number of carbon must be +4 to balance out the charges. **

The charge of 2 in CO3 comes from the combination of the individual charges of the elements involved. In the carbonate ion (CO3), the carbon atom has a charge of +4 and each oxygen atom has a charge of -2. When these charges are combined, the overall charge of the carbonate ion becomes -2. This charge allows the carbonate ion to form stable compounds with other elements. **

You can find out that CO3 is doubly negatively charged by looking at the chemical structure of the carbonate ion. The carbonate ion has a trigonal planar structure with a central carbon atom bonded to three oxygen atoms. Each oxygen atom has a formal charge of -2, and the carbon atom has a formal charge of +4. When you consider the resonance structures of the carbonate ion, you will see that the negative charge is delocalized over all three oxygen atoms, resulting in a doubly negative charge for the entire ion. This can be confirmed by calculating the formal charge of each atom and considering the resonance structures of the ion. **

SO4 is doubly negatively charged because it contains two extra electrons, giving it a total charge of -2. CO3 has a charge of -2, similar to SO4, as it also contains two extra electrons. PO4, on the other hand, has a charge of -3 because it contains three extra electrons. **

Molecules do not occur in all conceivable combinations of atoms because the arrangement of atoms in a molecule is determined by the chemical bonding between the atoms. This bonding is influenced by the number of available electrons in the outer shell of each atom, as well as the specific properties of the atoms involved. These factors dictate which atoms can form stable bonds with each other and in what ratios, leading to the formation of specific molecules. In the case of CO2, the carbon atom forms two bonds with oxygen atoms, resulting in a stable molecule. Conversely, CO3 or CO32 would not be stable configurations due to the inability of carbon to form stable bonds with three or more oxygen atoms. **

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