In (quasi) stable atoms the positive and negative charges form "charged" clouds, which can be represented as fractionally charged sub-clouds. In order to observe them as such, we have to have the same atomic state in the in- and out-states, i.e., we have to deal with elastic scattering in the first Born approximation. Then no atomic "polarization" effects are present. Let us consider for simplicity a large-angle scattering, i.e., scattering from the positive-charge sub-clouds (see formula (3) in this paper and here):
scattering amplitude∝∫|ψnlm(→ra)|2eimeMA→q∑→radτ
This integral is just a sum of integrations over different sub-clouds. If one manages to prepare the target atoms in a certain polarized state |n,l,m⟩ (in order not to average over different lz projections), the resulting cross section will be an elastic cross section of scattering from fractionally charged atomic sub-clouds. However, and let us not forget it, this will be an inclusive (or deep inelastic) scattering with respect to the soft photon emissions, which carry away a tiny portion of the total transferred energy/momentum |→q|.
Such fractionally charged sub-clouds are confined in atoms and are never observed independently of atoms, just like quarks. I wonder whether this analogy between quarks and the "usual" sub-clouds is deep or superficial, to your opinion.