Some atoms will interact to combine and from new substances. Atoms that interact in this way are said to be chemically "bonded". Whether atoms will interact to form chemical bonds depends almost entirely on their electron arrangement.
The electrons in the outer energy level can be called valence electrons. It is these electrons that determine the formation of chemical bonds. There are certain numbers of valance electrons that are more stable than others. Atoms will gain or lose electrons in order to become more stable. Atoms with eight valence electrons are the most stable.
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