atomic spectra

[josephyim1L]

Hi,

Can someone explain to me the whole concept behind electrons being excited to higher energy levels? I understand that incoming EM radiation excites an electron to a higher energy level, but Monday's lecture revolved around "ejecting" electrons. What is the difference between ejecting electrons and exciting them to a higher state and how does this difference play out?

[ian_haliburton_1f]

Certain amounts of energy from incoming photons will excite the electrons and cause them to move to higher energy levels. Beyond a certain point, however, the electron can move far enough away from the positive nucleus that the attractive force can no longer keep it in orbit. It is when there’s enough energy to cause this that the electron can be ejected, leaving the atom ionized.

[A De Castro 14B 2H]

Exciting an electron (such as that in hydrogen) to a higher energy level means moving it from say n=1 to n=2, given that the frequency of the incoming light that the electron absorbs matches the energy difference between n=1 and n=2. That electron will stay in its "excited state" at n=2 for a short period of time, and then transition back to its ground state at n=1, emitting energy as it does so. On the other hand, ejecting an electron means that it moves from say n=1 to n=infinity, which requires a lot more energy. At n=infinity, that photoelectron will have no energy (E = 0J), since it's essentially not interacting with the atom anymore.