Therefore, energy is proportional to the square of the atomic number divided by the square of the principal quantum number: \[ E \propto \frac{Z^2}{n^2} \]. The energy of the second orbit is: \[ E_2 = \frac{-13.6}{4} = -3.4\, \text{eV} \]. The energy difference for the transition from the second to the first orbit is: \[ \Delta E_{2 \to 1} = 10.2\, \text{eV} \]. Consequently, the only possible transition is from the state where \( n = 2 \) to the state where \( n = 1 \).
