Figure 13-12 Magnetic Interactions in the Hydrogen Atom (a) The energy of a pair of magnets is high when their north poles or their south poles are near each other, and low when they have opposite poles near each other. (b) Thanks to their spin, electrons and protons are both tiny magnets. When the electron flips from the higher-energy configuration (with its spin in the same direction as the proton’s spin) to the lower-energy configuration (with its spin opposite to the proton’s spin), the atom loses a tiny amount of energy and emits a radio wavelength photon at 21 cm.