2. 4.4 Unstable Nuclei and Radioactive Decay

3. Radioactive decay In the late 1890s, scientists noticed some substances spontaneously emitted radiation, a process they called radioactivity.radioactivity

4. Radioactive Decay Nuclear reactions can change one element into another element.

5. Radioactive decay Radiation is rays and particles given off. Reactions in a nucleus is nuclear reactions.

6. Unstable nuclei Elements that give off radiation are trying to make themselves more stable. They need a form where it does not take effort to exist

7. Nuclear Chemistry “Bravo” Test 1954 – 15,000 kilotons Video

8. Alpha Particles Alpha particles contain 2 p + and 2 n. Alpha radiation is alpha particles being given off.

9. Alpha radiation The atomic number decreases by 2, and the mass number decreases by 4.

10. Alpha Equation

11. Beta Radiation Each beta particle is an electron with a 1– charge.beta particle

12. Beta Radiation Beta emission converts a neutron to a proton Beta emission converts a neutron to a proton The mass number remains the same, but the atomic number increases by one. The mass number remains the same, but the atomic number increases by one.

13. Beta Equation

14. Electric Field Deflection

15. Gamma Rays Gamma rays are high- energy radiation with no mass and are neutral.Gamma rays Gamma rays account for most of the energy lost during radioactive decay.

16. Characteristics of Radiation

17. Unstable atoms Atoms that contain too many or too few neutrons are unstable and lose energy through radioactive decay to form a stable nucleus. Few exist in nature—most have already decayed to stable forms.

19. Types of Radioactive Decay  alpha production (  He): helium nucleus  beta production (  e):  gamma ray production (  ):  alpha production (  He): helium nucleus  beta production (  e):  gamma ray production (  ):

20. Specifying Isotopes 19 X A Z X = the symbol of the element A = mass number (protons + neutrons) Z = the atomic number (number of protons)

21. Nuclear Symbols Element symbol Mass number, A (p + + n o ) Atomic number, Z (number of p + )

22. Key to Balancing Nuclear Equations In nuclear reactions, both the atomic number Z and the mass number A must be conserved

23. Balancing Nuclear Equations 226 = 4 + ____ 222 88 = 2 + ___ 86 Atomic number 86 is radon, Rn Rn

24. Alpha Decay Alpha production (  ): an alpha particle is a helium nucleus Alpha decay is limited to heavy, radioactive nuclei

25. Alpha (α) Decay E1E1 P+N P P-2 + He 4 2 E2E2 P+N -4 an alpha particle (helium nucleus) is produced

26. Alpha Radiation Limited to VERY large nucleii.

27. Example of Alpha Decay Ra 222 88 86 + He 4 2 Rn Radium 222 decays by α particle production to Radon 218 218

28. Beta Decay Beta production (  ): A beta particle is an electron ejected from the nucleus Beta emission converts a neutron to a proton

29. Beta (β) Decay Beta emission converts a neutron to a proton E1E1 P+N P P+1 + e 0 E2E2 P+N

30. Beta Radiation Converts a neutron into a proton.

31. Example of Beta Decay Notice the mass of the beta particle is zero; it is so small that is must be neglected. C 14 6 7 + e 0 N 14

32. Example of Beta Decay Th 234 90 91 + e 0 Pa 234 Thorium 234 decays by β particle production to Protactinium 234 (notice: no change in mass number A, and an increase of 1 in atomic number Z)

33. Gamma Ray Production Gamma ray production (  ): Gamma rays are high energy photons produced in association with other forms of decay. Gamma rays are massless and do not, by themselves, change the nucleus

34. Gamma Ray Production Gamma ray production (  ): Gamma rays are high energy photons produced in association with other forms of decay. Gamma rays are massless and do not, by themselves, change the nucleus