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Periodic table
An arrangement of chemical elements in order of increasing atomic number. Elements of similar properties are placed one under the other, yielding groups or families of elements. Within each group, there is a variation of chemical and physical properties, but in general, there is a similarity of chemical behavior within each group. (See an online periodic table.)
Page Last Reviewed/Updated Thursday, August 27, 2026
Page Last Reviewed/Updated Thursday, August 27, 2026