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10/07/03 |
            
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In 1869. Dmitri Mendeleev found that when elements are arranged in order of
increasing atomic weight, properties reoccur in a periodic (repeating)
fashion. In columns he placed elements that had similar chemical and
physical properties. In 1913 Henry Moseley discovered the concept of
atomic numbers. The modern periodic table is arranged in order of
increasing atomic number. Some important vocabulary: Periods - the rows on the periodic table. Groups or Families - the columns on the periodic table. Most of the elements are metals, which are located on the left side of the table. Nonmetals appear on the right side of the table. In a narrow band between the metals and nonmetals are the metalloids or semimetals.
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This site was last updated 09/29/03
