| 1. 1 | 4. 1 | 7. 4 | 10. 2 | 13. 3 | 16. 4 |
| 2. 3 | 5. 1 | 8. 1 | 11. 3 | 14. 3 | 17. 3 |
| 3. 1 | 6. 4 | 9.4 | 12. 2 | 15. 3 | 18. 2 |
19. fission, some mass is converted into energy, fusion
20. 42He 21. radiation can change the structure of dna causing cancer
22. Calcium and radium both have 2 valence electrons
23. ZnS acts as a scintillator
24. ZnS is insoluble in water
25. radium causes cancer
26. 226Ra ----> 222Rn + 4He atomic numbers should be 88,86,2
27. radium and calcium both have 2 valence electrons
28 1600 yrs 1 g to 0.5 g is only 1 half life, look up in table N