Why can we not write a Lewis structure for carbon monoxide?

1 Answer
Dec 6, 2017

That is news to me.....

Explanation:

What follows is of course a FORMALISM, but molecular structure corresponds to such formalism....we draw the Lewis structure taking into account that we gots 4 valence electrons from carbon, and 6 valence electrons from oxygen to distribute, i.e. 5 electron pairs...

And thus we get a Lewis structure of ....

#""^(-):C-=O:^(+)#...i.e. 7 electrons around carbon, and 7 electrons around oxygen (note that I include the 2 inner shell electrons, i.e. the #1s^2# pair of each participating atom). And this Lewis structure leads to the assignment of a formal negative charge on carbon, and a formal positive charge on oxygen.

We could write #:C=stackrel(ddot)O:#, the which has no charge separation, ...inorganic chemists tend to prefer the FORMER representation in that carbon monoxide, which is an ubiquitous ligand in coordination chemistry, invariably (well almost) binds to the metal thru the carbon centre, and not the oxygen centre...i.e. the carbon is the donor, and thus is conceived to bear the negative charge.