Answer
The element emitting photons of highest energy is Au.
The element emitting photons of lowest energy is Na.
Work Step by Step
From the formula $$E=h\nu=h\frac{c}{\lambda}$$
we find that the energy of an emitted photon is inversely proportional with the wavelength of the emitted light.
In other words, the lower the wavelength of the emitted light, the higher the energy of the emitted photon. And vice versa.
Therefore, the element emitting photons of highest energy is the one with the lowest characteristic wavelength, which is Au $(267.6nm)$.
The element emitting photons of lowest energy is the one with the highest characteristic wavelength, which is Na $(589.6nm)$
