Atomic Structure & Periodic Table

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Across
  1. 3. Noble gas used in balloons
  2. 5. Element in Group 7
  3. 6. Element with atomic number 12
  4. 7. Russian scientist who created the periodic table
  5. 9. Vertical columns in the periodic table
Down
  1. 1. Atoms of the same element with different neutron numbers
  2. 2. Group 1 metals
  3. 4. Total number of protons and neutrons
  4. 8. Subatomic particle with a negative charge