Atomic Model/ Theory Crossword

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Across
  1. 1. The electrons in the outermost orbital are called the ______ electrons.
  2. 3. Which subatomic particle has a positive charge?
  3. 4. On the nuclear symbol, what do the letters in the middle represent?
  4. 6. What is a negative ion?
  5. 7. What are negatively charged particles?
  6. 9. What is atomic mass measured in?
  7. 14. Dalton proposed his atomic theory through a series of what?
  8. 15. Which subatomic particle has a neutral charge?
  9. 16. What is an atom that has an overall charge because it does not contain the same number of protons and electrons?
  10. 17. Who hypothesized that all matter and its behavior could be explained by tiny indivisible particles?
  11. 19. Who discovered the electron?
Down
  1. 2. On the nuclear symbol, what do the numbers on top represent?
  2. 5. What is the smallest unit of an element?
  3. 8. What is a positive ion?
  4. 9. On the nuclear symbol, what do the numbers on the bottom represent?
  5. 10. Scientists now think of electrons as occupying ______, not orbits.
  6. 11. In which process do atoms disintegrate by releasing smaller particles?
  7. 12. What is the center of an atom called?
  8. 13. Who first had evidence of the existence of atoms?
  9. 18. What are atoms made of the same element but with different mass numbers?