Richard Feynman didn't really focus on a specific "when" atoms attract each other, as he was more interested in the *why* and *how*. He emphasized the quantum nature of atomic interactions, which is more complex than a simple "when" statement.

Here's what we can glean from Feynman's lectures and understanding of atomic interactions:

* Atoms attract each other due to electromagnetic forces. These forces are mediated by the exchange of virtual photons. Feynman's work helped explain the "mechanism" behind this interaction, not just the fact of attraction.

* The attraction depends on the specific atoms involved. Different atoms have different electron configurations and therefore different interactions.

* Attraction can occur at different distances. At very short distances, repulsive forces dominate due to electron-electron interactions. At longer distances, the attraction due to the nucleus and electrons can overcome this repulsion, leading to bonding.

Instead of a specific "when," we can say that atoms attract each other when the balance of electromagnetic forces favors attraction. This balance depends on the specific atoms, their distance, and their orientations.

In summary: Feynman's focus was on the underlying mechanisms of atomic interactions, not on specific conditions of attraction. He explained how electromagnetic forces play a role in creating both attraction and repulsion between atoms.