# Why is carbon dioxide a Lewis acid? [duplicate]

I know this has been asked before, but can anyone explain me in simpler terms? Why is $$\ce{CO2}$$ a Lewis acid? The carbon atom doesn't have any vacant orbitals to accept a lone pair. How can it be a Lewis acid?

Suppose one of the doublets of one C=O bond moves to one of these two atoms. It will not be to the Carbon atom. The Oxygen atom is a better choice. And now this Oxygen atom would be negatively charged. As a consequence the Carbon atom is positively charged and has a vacant orbital able to accept a lone pair, for example from an $$\ce{OH-}$$ ion or from water. This will produce the ion $$\ce{HCO3^-}$$ (from $$\ce{OH-}$$) or $$\ce{H2CO3}$$ (from $$\ce{H2O}$$).