Why is #CO_2# a nonpolar molecule, whereas #CO# is a polar molecule?

1 Answer
anor277
Jan 23, 2017

Consider the vector sum of the individual bond dipoles........

Explanation:

The #C-O# bond in both gases is polar to a certain, limited extent. #""^(+delta)C-=O^(delta-)# has some polarity; on the other hand, for #""^(delta-)O=^(delta+)C=O^(delta-)#, the vectors of the bond dipoles clearly sum to ZERO.

This polarity is not reflected in the boiling points of the 2 gases, #-191.5^@# for #CO# at #1*atm#, versus a normal sublimation point of #-78^@C# for carbon dioxide, however, carbon dioxide is a bigger molecule, with extra dispersion forces.

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