Imagine that an electron in an excited state in a nitrogen molecule decays to its ground state, emitting a photon with a frequency of 8.88×1014 hz . what is the change in energy, δe, that the electron undergoes to decay to its ground state? express your answer in electron volts to three significant figures.

Since energy cannot be created nor destroyed, the change in energy of the electron must be equal to the energy of the emitted photon.

The energy of the emitted photon is given by:

where
h is the Planck constant
f is the photon frequency
Substituting , we find


This is the energy given to the emitted photon; it means this is also equal to the energy lost by the electron in the transition, so the variation of energy of the electron will have a negative sign (because the electron is losing energy by decaying from an excited state, with higher energy, to the ground state, with lower energy)