Ailea's Crossword

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Across
  1. 4. Early model describing atoms as indivisible particles
  2. 7. Atoms of the same element with different numbers of neutrons
  3. 9. Chart organizing elements by atomic number and properties
  4. 10. Neutral subatomic particle in the nucleus
  5. 12. Standard unit for measuring atomic mass
  6. 13. Number of protons in an atom
Down
  1. 1. Weighted average of all isotopes of an element
  2. 2. Positively charged particles in the nucleus
  3. 3. Vertical column on the periodic table
  4. 5. Center of an atom containing protons and neutrons
  5. 6. Negatively charged subatomic particle
  6. 8. NUMBER Sum of protons and neutrons in an atom
  7. 9. Horizontal row on the periodic table
  8. 11. Stream of electrons used in early atomic experiments
  9. 12. Smallest unit of an element