Energy Levels and Spectral Lines

This web tool presents the energy level structure and the spectra (emission and absorption) of a simplified atom. In this toy atom, there are only 4 energy levels. In real atoms, there can be many thousands of energy levels. Emission and absorption lines in the atom correspond to an electron (or electrons collectively) losing or gaining energy by jumping between energy levels.

Directions: By sliding the 3 excited energy levels (not the ground level), the spectral lines corresponding to transitions to and from that energy level will change in response.




Questions to Consider:

1. Consider a single spectral line. What happens to the energy of the light emitted or absorbed when the separation between the energy levels decreases? (Click for Answer)

The energy gained or lost is the difference between the energy of the upper level and the energy of the lower level. If the upper energy level has only a little more energy than the lower level, these two energy levels would appear close together in the energy level diagram. Little energy would be gained or lost in a transition between these closely spaced energy levels. Low-energy light would be absorbed or emitted during this kind of transition.

2. Consider a single spectral line. What happens to the frequency of the light emitted or absorbed when the separation between the energy levels decreases? (Click for Answer)

From Question 1, we know the energy of the light decreases. This also means that the frequency must decrease as well. Mathematically, energy and frequency are related by the equation E = hf. ("h" is Planck's constant)

3. Consider a single spectral line. What happens to the wavelength of the light emitted or absorbed when the separation between the energy levels decreases? What happens to the color of the spectral line? (Click for Answer)

Energy and frequency decrease when the energy levels are closer together (Question 1 and 2). Light of lower frequency has longer wavelength. This corresponds to redder light or infrared light.

4. Imagine an electron absorbed enough energy to jump from the ground level to the top energy level. What happens to the electron if it absorbs much more energy? What happens to the atom? (Click for Answer)

If an electron is given enough energy, it can escape the atom. This process is known as ionization. The electron is no longer bound to the atom. In the process, the atom loses the electron and becomes an ion. The atom is said to be ionized. Since large energies are related to large temperatures, ionized gases tend to be very hot.

5. Imagine an electron absorbs enough energy to jump from the ground level up to the first excited energy level. If the electron absorbs no more energy for a long time, what happens to the electron? (Click for Answer)

Left to itself, the electron will lose the energy it absorbed by emitting it. This emitted photon will have the same energy as the absorbed photon.



Created by Kevin Healy, 2007