Nuclear Reactions

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Across
  1. 2. — Most penetrating radiation; blocked by lead
  2. 3. — The smallest particle of an element
  3. 9. — How far radiation can travel through material
  4. 13. — An unstable isotope that emits radiation
  5. 16. — Low-level radiation naturally present everywhere
  6. 18. — Weakest radiation; stopped by paper
  7. 20. — The process of building new nuclei inside stars
  8. 21. — Using Carbon-14 to find the age of ancient objects
Down
  1. 1. — How the Universe began 13.8 billion years ago
  2. 4. — An unstable nucleus breaking down and releasing radiation
  3. 5. — Everything that exists; space, matter, and energy
  4. 6. — Positively charged particle in the nucleus
  5. 7. — Medium radiation; stopped by aluminium
  6. 8. — Negatively charged particle orbiting the nucleus
  7. 10. — Neutral particle found in the nucleus
  8. 11. — When radiation knocks electrons off atoms
  9. 12. — Energy or particles emitted from an unstable nucleus
  10. 14. — Time for half a radioactive sample to decay
  11. 15. — A heavy nucleus splitting in two, releasing energy
  12. 17. — Two nuclei joining together, powering the Sun
  13. 19. — Same element, different number of neutrons