How would you determine the formal charges on each atom in the carbonate ion (CO_3^(2-))?

1 Answer
anor277
Jul 8, 2016

CO_3^(2-) has 3xx6+4+2=24" valence electrons" to distribute around 4 centres.

Explanation:

Clearly I got the number of electrons from the atomic numbers of each element, and added 2 electrons to represent the charge. The charge lies on the most electronegative atoms, i.e. the oxygen atoms.

A Lewis structure of O=C(-O^-)_2 gives a neutral doubly oxygen, a neutral carbon, and 2 anionic oxygen atoms associated with 7 valence electrons. Of course, I can draw resonance structures to show the equality of the oxygen atoms.

See here for another example that demonstrates assignment of formal charge.

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