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

1 Answer
Jul 8, 2016

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


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.