Imagine two hydrogen atoms(each with one proton and one electron) approaching one another so that their electron clouds overlap(Figure 2.9). Once they meet, the electron configuration will change so that both electrons will primarily occupy the space between the atoms. In other words, the two electrons are shared by both hydrogen atoms and attracted simultaneously by the positive charge of the proton in the nucleus of each atom. The attraction between the electrons and both nuclei holds these atoms together. Although ions do not exist in hydrogen molecules, the force that holds these atoms together arises from the attraction of oppositely charged particles-protons in the nuclei and electrons shared by the atoms.