How do you calculate the formal charge of #CO_2#?

Question

Avery Adams · Accepted Answer

Do you mean #CO_2# or #CO_3^(2-)#?

None of the atoms in our representation of the #O=C=O# molecule bear a formal charge. For carbon and oxygen, #Z=6# and #Z=8# respectively, i.e. there are 6 and 8 formal positive charges in the carbon and oxygen nuclei. For neutrality, the carbon and oxygen atoms must also be each associated with 6 and 8 formal negative charges. Around oxygen there are 2 lone pairs (i.e. 4 electrons), and the oxygen has a half share in the four electrons that constitute the #O=C# bond. That's #4+2+2" (inner core)"# electrons; 8 electrons in total, and thus #O# is electrically neutral. Carbon shares 4 electrons from the double bonds, and with its 2 inner core electrons, has the required 6 electrons, 6 formal negative charges to balance the 6 positive nuclear charges.

Cooper Anderson · Answer

undefined To calculate the formal charge of CO2, you use the formula:

Formal charge = (Number of valence electrons in the free atom) - (Number of lone pair electrons) - (Number of bonds)

For carbon dioxide (CO2):
Number of valence electrons in carbon = 4
Number of valence electrons in oxygen = 6

Carbon has 4 valence electrons, and in CO2, it forms two bonds with oxygen atoms. Each oxygen atom contributes 2 electrons to each bond, so there are 4 bonding electrons around carbon. There are no lone pairs on carbon in CO2.

Formal charge on carbon in CO2 = 4 - 0 - 4 = 0

Each oxygen atom has 6 valence electrons and forms two bonds with carbon. Each oxygen atom also has two lone pairs.

Formal charge on each oxygen atom in CO2 = 6 - 4 - 4 = 0