The atoms bond because there is a strong enough attraction in both directions and room for the electrons in the outer energy level of the atoms. When two hydrogen atoms and an oxygen atom get close ...

The two collaborations combined their complementary data on the proton's inner structure ... The overall energy level of hydrogen depends on the spin orientation of the proton and electron.

Thus when an atom absorbs or gives off energy (as in light or heat), the electron jumps to higher ... of light emitted by real hydrogen atoms. Bohr's theory that electrons existed in set orbits ...