Let's consider now an electron from the valence shell.
As I mentioned before you can remove it from its laziness status to bring it into a more active one. If you offer it some radiation having appropriate energy it jumps from one energy level to another. This process is known as absorption of electromagnetic radiation. I really don't know why people say that I am excited after the absorption occurs, because the electron is the one excited not me. However it doesn't like to be excited and after a short time it jumps back to the original orbital, throwing away the extra energy as heat.
The electron may be excited by using heat instead of electromagnetic radiation. Again it jumps from one energy level to another where doesn't stay long. When jumping back the extra energy is thrown as electromagnetic radiation, phenomenon called emission of electromagnetic radiation.
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