Original: (typically between 1 eV and 103 eV), where is the Rydberg constant, Z is the Atomic number, n is the principal quantum number, is Planck's constant, and c is the speed of light.
Simplified: where is the Rydberg constant (typically between 1 eV and 103 eV), Z is the charge of the atom's nucleus, is the principal quantum number, e is the charge of the electron, is Planck's constant, and c is the speed of light.