Energy Level Diagrams

More about the Energy Model of the Hydrogen Atom

Up to this point, we have learned that light is produced when electrons make transitions in atoms. If they have high energy, they naturally lose it in the form of light as

they move to a lower energy level. In a normal situation the electrons will be in a low energy level. They must first be given energy to attain high energies so that it can

naturally lose that energy. An external energy source, such as electricity must supply that energy. This process is illustrated below.

Summary of Energy Levels for gases

The larger the external energy provided, the greater the number of electrons that will obtain higher energies. For example, suppose the energy difference between two allowed
energies is 2.55 eV. See the figure below. 

In other words, 2.55 eV must be supplied by the external source for a single electron to change from a low energy to a higher one. Supplying a larger amount of external energy
does not change the allowed energies. Recall that the allowed energies for an electron bound to an atom depend on the type of gas atoms found in the lamp. Supplying a larger
amount of external energy causes a larger number of electrons to possess the highest allowed energies. Thus, more electrons will make transitions from higher allowed energies
to lower allowed energies that result in the greater emission of photons and brighter light.

A different situation occurs if the energy supplied to the atom is not equal to the difference between energy levels. For the example illustrated above no transition will occur if
the atom receives less than 2.55 eV.  If the atom receives 2.40 eV of energy, it cannot use the energy.No energy level exists for that transition to occur. If it gets more than 2.55 eV but less than 5.10 eV of energy, only one electron can make the transition. When 3.20 eV is available, the electron may be able to use 2.55 eV and the remaining 0.65 eV will end up as some other form of energy (frequently as motion of the entire atom).

 
The electrical properties of an atom uniquely determine what energies its electrons are allowed to have. So, even though the Gas Lamp Spectroscopy computer program allows
you to adjust the energies available to the electrons, these energies are fixed at very specific values by the electrical properties of the atom.   Because these electrical properties are different for each of the chemical elements, the atoms of each of the elements have a unique set of energies. Thus, the light given by any hydrogen atom is the same as every other hydrogen atom.  However, that light is different from the ligth emitted by every helium atom. Thus the light emitted by a material can be used to determine the type of elements present. This property is used to learn about the composition of distant stars as well as substances on earth