A student of physics says: “an electron falls from an energy level of -4.5 eV to -7.2 eV. It emits a photon wi

A student of physics says: “an electron falls from an energy level of -4.5 eV to -7.2 eV. It emits a photon with 2.7 eV of energy”. Give your comment on his claim.

Hi Fahad, -4.5 eV is greater than -7.2 eV.
So as electron falls from higher energy level to lower energy then the excess energy would have been radiated as a photon
So the difference = final - initial
Hence - 2.7 eV
Negative sign indicates that the atom gives out that energy in the form of a photon.
Now think about this. The energy of the electron in case of hydrogen atom for the first orbit is -13.6 eV
As we supply energy of +13.6 eV to the atom, then energy of the electron comes to be 0.
This means that the electron has just come out of the atom. So +13.6 eV is ionization energy