The energy of two hydrogen atoms can be represented in a diagram such as that above. The horizontal axis indicates the distance between atoms in angstrom units, and the vertical axis indicates the energy, with lower energy and greater stability represented downward. The zero point of energy has been chosen to be that of two infinitely separated, noninteracting atoms.
Two hydrogen atoms infinitely far apart obviously do not interact, and thus have no bond between them.

As the atoms come closer together, little happens until their interatomic distance decreases to a few angstroms. Then the electron of one atom begins to be "seen" by the nucleus of the other. Each electron is attracted by the other nucleus, the electrons become concentrated between the nuclei, and a bond begins to form. The energy of the two atoms decreases as the attraction of each nucleus for the other electron becomes significant.