3. Mass-Energy Equivalence All matter is a form of stored energy.

4. Mass-Energy Equivalence All matter is a form of stored energy. If matter of mass m is converted to energy, the amount of energy E that can be released is equal to:

5. Mass-Energy Equivalence All matter is a form of stored energy. If matter of mass m is converted to energy, the amount of energy E that can be released is equal to: E = mc 2

6. Mass-Energy Equivalence All matter is a form of stored energy. If matter of mass m is converted to energy, the amount of energy E that can be released is equal to: E = mc 2 c = 3.0 x 10 8 m/s

7. Mass-Energy Equivalence: Example What is the energy equivalent of a 52 kg person?

8. Mass-Energy Equivalence: Example What is the energy equivalent of a 52 kg person?

9. Mass-Energy Equivalence: Example What is the energy equivalent of a 52 kg person?

10. The Mass Defect More practically, we look at the energy equivalent of the mass defect.

11. The Mass Defect More practically, we look at the energy equivalent of the mass defect.

12. The Mass Defect Consider a Carbon 12 nucleus:

13. The Mass Defect Consider a Carbon 12 nucleus: 6 protons, 1.007276 amu each + 6 neutrons, 1.008665 amu each = 12.095646 amu

14. The Mass Defect Consider a Carbon 12 nucleus: 6 protons, 1.007276 amu each + 6 neutrons, 1.008665 amu each = 12.095646 amu Actual mass of Carbon 12 nucleus: = 11.996709 amu

15. The Mass Defect The 0.098937 amu mass defect is the binding energy of the nucleus. E = mc 2 E ≈ (0.098937)(1.66 x 10 -27 kg)(3.0 x 10 8 m/s) 2 E ≈ 1.5 x 10 -11 J

17. Nuclear Decay Alpha Decay Beta Decay Gamma Decay Positron Emission Electron Capture

18. Discovery of Radioactivity Radioactivity is the release of energy or particles when an atom disintegrates (demo) Radioactivity was discovered when minerals were exposed to film through an opaque cover The 3 types of radioactivity can be shown by passing emissions through an electrical field: Lead block Radioactive substance Phosphorescent zinc sulfide detection screen + – Strong magnetic or electrostatic field   

19. Types of Radioactivity Types of radiation: 1) , 2) , 3)  1.Alpha (  ) particles are symbolized as 4 2 He 2.Beta (  ) particles (essentially electrons) are 0 –1 e 3.Gamma (  ) rays are symbolized as 0 0  You can determine the composition of each:  : mass of 4 u, charge of +2 (2 p +, 2 n 0, 0 e – ) Other symbols: proton = 1 1 p, neutron = 1 0 n There are different terms to describe the different types of nuclear reactions “alpha decay” means an  particle is given off. Other: beta decay, fusion (meaning to bring together), fission (meaning to break apart)

20. Alpha Decay Alpha decay occurs when a helium nucleus is emitted from the nucleus of an unstable atom, forming a new atom with a smaller mass. When an atom undergoes alpha decay, the atomic number of the atom decreases by two and the atomic mass decreases by four.

21. Alpha Decay In alpha decay/emission, a helium nucleus is emitted.

22. Alpha Emission In alpha emission, a helium nucleus is emitted. This reaction can be represented by an equation.

23. Alpha Emission In alpha emission, a helium nucleus is emitted. parent nucleus daughter nucleus alpha particle

24. Alpha Emission In alpha emission, a helium nucleus is emitted. mass number atomic number

25. Beta Decay Beta decay is when an electron (called in this context a “beta particle”) is emitted from the nucleus of an atom, while a neutron turns into a proton. As a result, the atomic number of the element increases by one, while the mass stays the same.

26. Gamma Decay Gamma decay is when very high energy light called gamma rays are emitted from a nucleus to bring it to a lower energy state. Gamma decay generally takes place at the same time as other nuclear reactions.

27. Positron Emission Positrons are the antimatter equivalent to electrons, so they have the same mass but a charge of +1. Positron emission is when a positron is given off by a nucleus. Positron emission causes the atomic number of the element to decrease but the atomic mass to stay the same.

28. Electron Capture Electron capture is when an electron is absorbed by the nucleus of an atom, causing the atomic number to decrease by one but the atomic mass stays the same.

30. Nuclear equations Q. Write the beta decay for C-14 In all cases, charge and mass must be balanced C 14 6  e 0 N 14 7 + Po 209 84  He 4 2 Pb 205 82 + Q. Write the alpha decay for 209 Po Q. Complete this fission reaction Kr 94 36 U 235 92  n 1 0 Ba 139 56 + n 1 0 + 3 +