Why Do Atoms Combine?

By Staff WriterLast Updated Apr 14, 2020 5:50:52 PM ET
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Atoms combine together when the outermost shell, or valence shell, of electrons is not filled with two electrons (if there is only one shell) or eight electrons (if it has more than one shell). Atoms combine to fill the outermost shell and become stable compounds by either losing electrons to become ions or gaining electrons. Atoms can combine with similar elements or different elements.