1. Radioactive Isotope Isotope which is unstable. It emits radiation & changes into another kind of atom.

2. Transmutation Reaction When one kind of nucleus changes into another kind of nucleus.

3. Stability Depends on neutron to proton ratio.

4. Which elements are unstable? All the elements with atomic number > 83 (or beyond Bismuth)

5. Types of Radiation Alpha, Beta, Gamma Separated by electric or magnetic fields.

6. Least penetration power Alpha radiation. Shielding can be paper or cloth.

7. Most penetration power Gamma radiation. Requires lead/concrete shielding.

8. 2 He or 2  Symbol for alpha radiation 4 4

9. 2 He or 2  Same as the nucleus of a helium atom 4 4

10. -1 e or -1  or  - or  Symbol for beta particle 00

11. -1 e or -1  or  - or  Fast moving electron originating from nucleus 00

12. +1 e or +1  or  + Symbol for positron. 00

13. 0  or  Symbol for gamma radiation. 0

14. 0 n or n Symbol for neutron 1

15. 1 H or 1 p Symbol for proton 1 1

16. Decay Mode When radioactive isotopes emit radiation, the decay mode is the type of radiation they emit.

17. Alpha Decay Unstable nucleus emits an alpha particle. Atomic #  by 2. Mass #  by 4.

18. 220 Fr  4  + 216 At Unstable nucleus emits an alpha particle. Atomic #  by 2. Mass #  by 4. 87 285

19. 220 Fr  4  + 216 At Natural Transmutation. 1 term on reactant side. 87 285

20. 220 Fr  4  + 216 At Balance nuclear equations using conservation of atomic number & conservation of mass number. 87 285 4 + 216=220 87= 2 + 85

21. 27 Al + 4 He  1 n + X Use conservation of atomic number & conservation of mass number. 13 0 1 + Y=27 + 4 13 + 2 = 0 + Z 2 Y Z So Y = 30 So Z = 15 Now have 30 X. Use PT. 15 X is P

22. Artificial Transmutation Particle “bullet” hits target nucleus & new isotope is produced. 2 terms on reactant side.

23. Artificial Transmutation 32 S + 1 n  32 P + 1 H 16015 1 bullettarget

24. Artificial Transmutation Particle “bullet” may be proton or alpha particle. To react with a nucleus, must overcome + + repulsive forces by accelerating bullet to high speeds. Particle “bullet” may be a neutron. Neutrons have no charge, so no repulsive forces to overcome. No acceleration necessary.

25. Fission Fission is division. Large nucleus (U-235 or Pu-239) is split into 2 medium sized nuclei by a neutron bullet. Excess neutrons & a great deal of energy are also produced.

26. 239 Pu + 1 n  90 Sr + 147 Ba + 3 1 n Fission 94003856

27. Fusion Fusion: U for unite and U for sun. Very small nuclei (H & He) are jammed together. Huge amounts of energy are released.

28. 1 H + 2 H  3 He Fusion 1 1 2

29. Identify each of the rxns a) 1 n + 235 U  142 Ba + 91 Kr + 3 1 n + energy b) 59 Co + 1 n  60 Co c) 3 He + 1 H  4 He + 0 e d) 14 C  14 N + 0 e 09256360 270 2 1 2+1 67 fission Artificial transmutation fusion Natural transmutation

30. Half-Life Amount of time required for ½ of a radioactive sample to decay. Each isotope has its own half-life. Not affected by temperature, physical or chemical environment, or age of sample. The shorter the half-life, the more radioactive.

31. Length of Half-Life Source: http://www.dlt.ncssm.edu/TIGER/chem2.htm#nuclear

32. # of Half-Lives = Time elapsed Half-life

33. Half-Life Map Fraction Remaining # of Elapsed Half-lives Mass Remaining 1 ½ ¼ 1 / 8 1 / 16 1 / 32 1 / 64 0 1 2 3 4 5 6 This line depends on the information in the problem. M initial or M final  Divide by 2  Multiply by 2

34. After 62 hours, 1.0 g remains unchanged from a sample of K-42. How much K-42 was in the original sample? Look up HL of K-42 in table N: 12.4 h Calculate number of HL: 62 hours = 5 HL 12.4 h/HL

35. Half-Life Map Fraction Remaining # of Elapsed Half-lives Mass Remaining 1 ½ ¼ 1 / 8 1 / 16 1 / 32 1 / 64 0 1 2 3 4 5 6 M initial or M final  Divide by 2  Multiply by 2 1.0 g 2.04.08.016.032.0

36. Problem 2 80 milligrams of a radioactive substance decays to 10 milligrams in 30 minutes. Calculate the HL. NOTICE: They gave BOTH masses. 80 mg  40 mg  20 mg  10 mg Took 30 min or 3 HL to decay to 10 mg, so 1 HL = 10 min.

37. Uses of Radioisotopes 1.C-14 dating of organic material 2.U-238 dating of rocks 3.Chemical tracers 4.Medical: use isotopes with short half-lives that are quickly eliminated from body. (I-131, Co-60, Tc-99) 5.Irradiation of food & mail