Chem – Electrons Moving Between Shells


How do electrons move between shells or energy levels?

VIDEO Explanation of electrons moving between shells.

With all this information about the position of the electrons compared to the nucleus in sections like electron shells and energy levels, we should also discuss how electrons can move from one shell or energy level to anther. In these next few sections I will use the words electron shells and energy levels to mean that same thing. Teachers can use either of those words to describe where electrons can move to. Make sure you understand both the sections on electron shells and energy levels before you go any further in this section.


So how do electrons move from one shell to the next? The explanation is actually quite simple. Let us discuss how an electron moves from a lower energy level to a higher energy level first. Electrons are negatively charged and move around the other edges of the atom, and protons are positively charged and are at the center of the atom (nucleus). That means that the negatively charged electron and the positively charged proton attract each other. So how do I move the electron away from the nucleus to a shell that is further away or to a higher energy level? Simple I expend energy or I put energy into the electron to do it. Pulling the electron away from the nucleus (center of an atom) requires the same kind of action just like moving an object off the floor against the force of gravity.


We can create a scenario that is easy to think about. I am going to use three objects or areas to describe it to you. Lets put a soccer ball on the ground. The ground represents the nucleus and the soccer ball represents the electron and the air above the ball represents higher energy levels. If I want to move the ball away from the ground and higher what do I do? I pick the ball up with my hands and move it away from the ground, but what is required for me to do that. I have to expend energy in my muscles and that energy gets stored in the ball. So moving the ball upward requires energy. The exact same requirements of energy are present when you move an electron away from the nucleus. In fact, the formula that allows us to calculate the force or energy between the electron and the proton (electromagnetic) is extremely similar to the formula that allows you to calculate the force or energy between the ball and the ground (gravity). Therefore, my analogy of the ball to the electron not only works well in thought, but also has mathematical proof behind it.


What if we now want to determine what happens when the electron moves from an outer shell or energy level to a lower shell or energy level? Again simple. We run the soccer ball analogy in reverse. If you are holding the soccer ball up high in your hands and you want it to move toward the floor what do you do? You drop it. What happens when you drop it? The ball moves toward the floor until something stops it and when the ball stops it lets out a sound. Sound is just a form or energy so all the ball is doing is letting go of some of its energy that was put into it when it became raised up. What does that mean the electron does? When the electron moves from a higher energy level to a lower energy level it must therefore give away some of its energy. However, the electron does not give away energy in the form of sound but in the form of light.


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