Chemistry cross-word puzzle

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Across
  1. 3. Who stated that electrons exist in specific energy levels?
  2. 5. An atom or group of atoms that has either gained or lost e- so that it is no longer electrically neutral.
  3. 8. Transition elements are all?
  4. 10. Who discovered protons?
  5. 11. What is the mass of an atom given in amu?
  6. 13. A transition of a substance directly from solid to gas.
  7. 15. a neutral particle having equal numbers of p+ and e-
  8. 18. The temperature and pressure at which the solid, liquid, and gas forms of a substance coexist.
  9. 19. Who stated the atomic theory?
  10. 20. Who discovered the neutron?
Down
  1. 1. Who used X-ray Technology to measure the nuclear change and atomic # of elements?
  2. 2. Who created the first Periodic Table?
  3. 4. Group 1 of the periodic table is called?
  4. 6. Who developed the ideas of photons?
  5. 7. What do all elements exist as?
  6. 9. Who discovered the nucleus of an atom?
  7. 12. What are positive charged ions?
  8. 14. What rule is it when atoms gain, lose, or share valence e- to attain a 8 valence electrons?
  9. 16. What is the lowest energy state of an atom?
  10. 17. What type of elements were - H, N, O, F, Cl, Br, I?