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After reading this section you will be able to do the following:

  • Describe the behavior of electrons in an atom.
  • Explain how electrons allow atoms to gain or lose energy.

So far, we have talked mainly about what is inside the nucleus of an atom. Protons and neutrons are found in the nucleus. Circling around outside the nucleus are tiny little particles called electrons. Electrons have a negative charge. Electrons spin as they circle the nucleus billions of times every second. They are moving so fast and the path that they travel is not the same each time, so that if we could see these electrons, they might appear to look like a cloud around the nucleus.

According to current theory, electrons are arranged in energy levels around the nucleus. When electrons gain or lose energy, they jump between energy levels as they are rotating around the nucleus. For example, as electrons gain energy, they might move from the second to the third level. Then, as they lose energy, they might move back to the second level or even to the first energy level. Only a certain number of electrons can be in an energy level at the same time.

The photon shown in the graphic can be considered a small bundle of energy

(For more information on atoms, you may want to review the materials on magnetism.)


  1. Electrons spin and rotate around the outside of the nucleus.
  2. As the electrons circle the nucleus they travel at certain energy levels but can "jump" between different energy levels if they gain or lose energy.