Assume that the Maxwell-Boltzmann distribution is valid in a gas of atomic hydrogen. What is the relative number of atoms in the ground state and first excited state at 293 K (room temperature), 5000 K (the temperature at the surface of a star), and 10^{6} K (a temperature in the interior of a star)?

**Strategy** The desired ratio is

In the ground state (n = 1) of hydrogen there are two possible configurations for the electron, that is, g\left(E_{1}\right)=2. There are eight possible configurations in the first excited state (see Chapter 7), so g\left(E_{2}\right)=8. For atomic hydrogen E_{1}-E_{2}=-10.2 eV. Therefore

\frac{n\left(E_{2}\right)}{n\left(E_{1}\right)}=4 \exp [\beta(-10.2 eV )]=4 \exp (-10.2 eV / k T)for a given temperature T. We need to insert numerical values for each of the temperatures.