INTERVIEWER: When two hydrogen atoms approach one another, weak attractive forces operate between them. As they approach more closely, their 1s orbitals overlap more extensively and covalent bond formation occurs. As the atoms move still closer together, the electron pair that forms the bond does not effectively screen the nuclei from one another, and nuclear-nuclear repulsion becomes more important. The minimum energy structure in which the nuclei are separated by 0.74 angstroms corresponds to the best compromise between nuclear repulsion and the attractive interactions between the electrons and the two nuclei.