Periodic Table of Elements

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Across
  1. 1. metal+metal
  2. 3. positively charged particle
  3. 6. tiny piece of everything
  4. 7. in the middle of an atom
  5. 8. has the same number of protons
  6. 9. a charged atom
  7. 10. number of protons of an atom
  8. 11. a unit of mass that describes the mass of an atom or molecule
  9. 12. zero charged particle
  10. 14. negatively charged particle
  11. 15. around the nucleus
  12. 17. holds quarks together
  13. 18. the number of groups in the Periodic Table
Down
  1. 2. the mass of an atom expressed in atomic mass units
  2. 4. the sum of the numbers of protons and neutrons in the nucleus of an atom
  3. 5. created the Periodic Table
  4. 9. metal+non-metal
  5. 11. makes up everything in the universe
  6. 13. an atom
  7. 16. non-metal+non-metal