Physics D
Across
- 3. radiation stopped by paper
- 4. radiation stopped by aluminium
- 6. contains neutrons and electrons
- 8. different forms of the same element
- 9. time taken to lose half of its radioactivity
- 14. constant low level environmental radiation
- 15. discovered electrons
- 16. person exposed to radiation
- 17. unwanted presence of radiation
- 19. negative charge
Down
- 1. discovered neutrons in the nucleus
- 2. said alpha particles deflected
- 5. unit measuring radiation
- 6. no charge
- 7. large, unstable nucleus that makes 2 smaller nuclei
- 10. same number of electrons and protons
- 11. 2 small nuclei join to make one large nucleus
- 12. radiation stopped by thick lead
- 13. positive charge
- 18. unequal number of electrons and protons