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1.                 From The Elements (07Nov00):
                   
   
   
                   
                     
   sodium
   Symbol: Na
   Atomic number: 11
   Atomic weight: 22.9898
   Soft silvery reactive element belonging to group 1 of the periodic table
   (alkali metals). It is highly reactive, oxidizing in air and reacting
   violently with water, forcing it to be kept under oil. It was first
   isolated by Humphrey Davy in 1807.