Electron transit in hydrogen atoms (II)

Published: 27 Oct, 2020 | Last modified: 27 Jan, 2022

In our previous post, we have successfully deduced the energy levels diagram in hydrogen atoms from the discrete line emission spectrum.

Now we'll look at some electron transits in hydrogen atoms with the help of the energy levels diagram.

First, we're going to supply energy to promote the electrons in \(E_1\) to \(E_6\). After we turn off the energy supply, the electrons in \(E_6\) may fall back to \(E_1\). At the same time, extra energy would be released by the electrons, in the form of photons.


Electron transit in hydrogen atoms: electrons promoted to energy level 6 by external power, and fall back to energy level 1 with light emitted

We could repeat the process with slightly less power supplied to the electrons. So the electrons may not be able to jump so high to \(E_6\), but they would jump to \(E_5\) instead.


Electron transit in hydrogen atoms: less energy provided so that electrons jump to energy level 5 only

Let's continue exploring by applying various power to the electron, so that it would jump to \(E_4\), \(E_3\), and \(E_2\), and would then fall back to \(E_1\). All these transitions result in emission of UV lights with different wavelengthes.


Electrons could fall back to energy level 1 from various energy levels

Besides the above senarios, electrons are able to transit to \(E_2\) or \(E_3\) from higher energy levels as well. However, the energy released will be much less and therefore, only visible lights and IR lights could be generated respectively.


Visible lights and IR lights are emitted when electrons transit from higher energy levels to energy levels 2 and 3 respectively

It seems our energy levels diagram could help us to understand the electron transit in hydrogen atoms, and we could predict and explain the experimental results with the help of the energy levels diagram. Great job!

But unfortunately, this energy levels diagram has its own limitation. We'll talk about that in our next post. Before we move on, we just want to answer some of the common questions.

Q: Do electrons have to follow these patterns when they transit between energy levels?

A: No. They don't have to. They could transit between any two energy levels either from low to high energy levels, or from high to low energy levels.

Q: Could other electromagnetic waves be produced?

A: Theoretically yes. But not for the hydrogen atoms that we're talking about. For hydrogen atoms, the electromagnetic wave with the highest energy is UV, while the light with the lowest energy falls in the IR category.

Q: What if an electron moves to \(E_3\) from a higher energy level?

A: In short, an IR electromagnetic wave will be produced.

Do take note that we're talking about electron transit according to Bohr's model, which is an oversimplified model. As we mentioned earlier, this model has its limitation. So the most important thing here is to understand the concept of energy level. We could simply say that UV will be produced as long as an electron transits to \(E_1\), visible light is seen when an electron moves to \(E_2\), and IR will be emitted for other energy levels. The actual experiment results could be different, but the concepts that we learn here apply.

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Authored by Chemistry: A Journey of Atoms on https://chemistry.kemistudio.com
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