Once again, a Lewis base is a molecule containing a pair of electrons, a pair of non bonding electrons in an orbital. So hydrant is an example of a Lewis base because it has two electrons, a pair of non bonding electrons within the one S orbital. Now, when the Lewis acid react with the Lewis base, that basically means their atomic orbitals interact. They overlap, producing a bond. So in this case, when this Lewis acid interacts with this Lewis base, this one S interacts with this two p.
These two electrons are donated to this two P orbital. Now, as these come closer, this load becomes smaller, this becomes larger so that the overlap is better.