Boltzmann equation

What
The ratio of the number of atoms in different states of excitation for neutral atoms is given by the Boltzmann Equation. This ratio is described as a function of temperature.

$$\frac {N_b}{N_a} = \frac {g_b}{g_a} e^{-(E_b - E_a)/kT}$$

Degeneracy

 * Hydrogen: $$g_n = 2n^2$$

Energy Levels

 * Hydrogen: $$E_n = - \frac {1}{n^2} 13.6 eV$$