History of the Periodic table

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Across
  1. 3. a group of three elements with similar chemical properties in which the relative atomic mass of the middle element is approximately equal to the average of the other two
  2. 4. The Law of ______ states that when elements are arranged in order of increasing atomic mass their properties repeat every eight elements.
  3. 6. ______ rearranged the periodic table in order of increasing atomic number.
  4. 9. chlorine, _______ and iodine are an example of a triad
Down
  1. 1. The modern periodic law states that when elements are arranged in order of increasing atomic ______, the properties of elements recur periodically.
  2. 2. Mendeleev left gaps in his periodic table to leave room for ________ elements with similar properties in the group.
  3. 5. predicted that elements combined together in chemical reactions to form what are now called compounds.
  4. 7. a substance that cannot be split into simpler substances by chemical means
  5. 8. Mendeleev’s _______ law states that when elements are arranged in order of increasing atomic mass the properties of elements recur periodically.