Polarization, donor-acceptor interactions, and covalent contributions in weak interactions: a clarification.

The concepts of polarization (induction), charge transfer and covalent bonding contributions are discussed in terms of weak interactions. They are shown to be different incarnations of the same phenomenon, so that using polarization to describe them is most consistent as it is the only real, measurable and uniquely defined quantity of the three. Dispersion is discussed as a form of polarization within the Feynman description. Model calculations are described. Graphical abstract The electron density of a hydride ion (nucleus white) polarized by a single positive point charge (brown).