Atomic Structure and Isotopes

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Across
  1. 6. the Russian chemist who published the first periodic table
  2. 9. are found on the right side of the periodic table and tend to gain electrons
  3. 11. vertical columns on the periodic table
  4. 12. the sum of the number of protons and neutrons
  5. 13. the charge of a neutron
Down
  1. 1. subatomic particle that is negatively charged
  2. 2. the elements of the periodic table were organized by Mendeleev in order of increasing __________
  3. 3. alkali metals tend to ______ lose electrons, forming positive ions
  4. 4. group 18 elements are known to be _______ or non-reactive
  5. 5. the number of horizontal rows on the periodic table
  6. 7. the center of an atom
  7. 8. the atomic number is equal to the number of protons
  8. 10. same elements with different numbers of neutrons