Here, it is assumed that the proton-electron interaction is one-to-one. The force exerted on an electron by other protons is shielded by the other electrons. As shown in Tab. 2, the temperature is in the order of 10 4 -10 5 K. The active elements give the low temperatures. For example, from Li to Ne, the temperature of surface electrons increases from 3.33×10 4 to 1.463×10 5 K. As expected, the temperature of electrons is much higher on the inner orbits due to the smaller radius. Correspondingly, the velocity of surface electrons is in the order of 10 3 km/s. As we know, the photon speed is 3.0×10 5 km/s. Given that light is a type of heat transfer by which a hot electron transfers heat to a cold electron, considering the acceleration of heat transfer (Eq. 35), it implies a possibility that the photon speed is not constant, but 3.0×10 5 km/s is a limitation of the measuring method, which substantially depends on the response speed of electrons. Moreover, the kinetic energy of surface electrons approximately equals the first ionization energy of elements. However, it is worth discussing because, according to heat transfer Eq. 3, the ionization energy includes the system's work. As an electron is removed from an atom, the proton-electron interaction is enhanced because the shielding effect is weakened.