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| | Periodic table - Wikipedia, the free encyclopedia |
 | | A group, also known as a family, is a vertical column in the periodic table of the elements. |
 | | The periodic table of the chemical elements, also called the Mendeleev periodic table, is a tabular display of the known chemical elements. |
 | | The original table was created without a knowledge of the inner structure of atoms: if one orders the elements by atomic mass, and then plots certain other properties against atomic mass, one sees an undulation or periodicity to these properties as a function of atomic mass. |
| en.wikipedia.org /wiki/Periodic_table (1487 words) |
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