# How would you calculate the formal charge of CO2?

Nov 6, 2015

#### Answer:

Carbon dioxide, as you know, is formally neutral; its constituent atoms are all also formally neutral.

#### Explanation:

$: : O = C = O : :$ is the typical Lewis structure. When we assign charge we conceive that a covalent bond is shared by the 2 participating atoms. Therefore, the central carbon shares 4 electrons with the oxygens; there are 2 inner core electrons, and thus on $C$ there are 6 electrons that balance the 6 positively charged protons of the carbon nucleus. Carbon is neutral. For oxygen, $Z = 8$, there are 2 lone pairs ($4 \times {e}^{-}$) whose charge devolves solely on $O$, 2 ${e}^{-}$ from the double bonds (i.e. again $\frac{1}{2}$ of the bonding electrons), and 2 inner core electrons. Thus these 8 electrons in total balance the nuclear charge.

Can you do the same thing with nitrate anion, $N {O}_{3}^{-}$? Where does the formal negative charge lay (there is also a formal positive charge!).