1. 1 Atomic Physics

2. 2 In 1896 Henri Becquerel discovered that certain uranium compounds would fog photographic plates as if exposed to light. He discovered that a magnetic field could deflect the radiation that caused the fogging.

3. 3 Marie and Pierre Curie investigated further. They discovered that thorium is also radioactive, and discovered two new elements: radium and polonium (named for Marie’s native Poland). Marie coined the term radioactivity.

4. 4 Alpha: the emission of a helium nucleus (an alpha particle): Beta: the emission of a high energy electron: Gamma: the emission of a high energy photon:

5. 5 Heads Up! Guaranteed exam Question

6. 6 Charge: Net charge remains constant: total charge of the reactants = total charge of the products. Atomic mass number: The total atomic mass number for the products = total atomic mass number for the reactants.

7. 7 A. Is this reaction possible? 1. Charge: (p + are +) + 90 = + 88 + + 2 (charge is balanced) 2. Atomic mass number: 230 = 226 + 4 (N is balanced) The reaction is possible.

8. 8 B. Is this reaction possible? neutron 1.Charge: + 27 ≠ + 28 + 0 (charge not balanced) 2. Atomic mass number: 60 = 60 + 1 (N not balanced) The reaction is not possible.

9. 9 1. alpha ( α ) – spontaneous emission of an alpha particle by a large, unstable nucleus. consists of 2 protons and 2 neutrons cannot penetrate more than a sheet of paper ionize atoms they collide with low biological hazard Alpha Decay

10. 10  In a large nucleus, the electrostatic force pushing p+ apart is nearly as strong as the attractive strong force, making the nucleus unstable.  An alpha particle (2 p+ and 2 n°) is a very stable configuration, so alpha particles are emitted not individual p+or n°.  In alpha decay, Z decreases by 2, and A decreases by 4.

11. 11  In general:  Example: Parent element Daughter element

12. 12  Write the alpha decay process for polonium- 210.  Name the parent and daughter elements. Parent element: polonium Daughter element: lead

13. 13  Mass defect, and mass-energy equivalence can be used to determine the maximum E k an emitted alpha particle will have.

14. 14  Write the alpha decay process for the decay of radium-226.  Use the data on page 881 to determine the mass defect in the reaction, and its energy equivalence. This energy will be the maximum E k an alpha particle could have in the reaction.

15. 15  Parent element:daughter element: radiumradon

16. 16 Note: if Δm were negative, this means no energy was released, so the decay would not happen.

17. 17  Most of this energy will be E k of the alpha particle.

18. 18  A neutron emits a beta particle (an e¯)  and becomes a proton.  penetrate up to 3mm of aluminum, 500 sheets of paper  produces burns to skin or tissue the antiparticle of beta particle is a positron

19.  Z increases by 1, and A does not change.  The transformation of a neutron into a proton involves the weak nuclear force, a fundamental force 19 Beta particle

20. 20  most harmful because it penetrates through most matter  penetrates the living cells, breaks down DNA bond resulting in cancer growths, mutations in offspring  uses – radiation therapy, irradiate foods, fruits

21. 21 146 n 92 p Gamma radiation n = 1 n = 2 e

22. 22  -stable isotopes have the same number of protons and neutrons  -elements with more than 83 protons are unstable and transmutate into stable nuclei with higher binding energies

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24. 24  occurs when the electromagnetic force within a nucleus is as great or slightly greater than the strong nuclear force  during the decay, momentum, energy ( mass energy) and charge are conserved Eg) Mass is conserved 238=238 Charge is conserved 92=92

25. 25  14 decays lead (stable)

26. 26 A. Beta negative decay  A nucleus decays emitting an electron, beta negative or β decay  A neutron within a nucleus transforms into a proton

27. 27  The daughter nucleus has more mass than the electron and the energy released goes into the kinetic energy  The β particle has less E k than expected and this missing energy is carried away by a neutral particle called a neutrino, v, and its mass and size are unknown  β decay involves a weak nuclear force acting on electrons and neutrinos and antimatter Note: Antimatter – matter that has a charge opposite to that of ordinary matter

28. 28  The antimatter of the electron is a posit ron,  The antimatter of a neutrino ( v ) is an antineutrino ( ) Eg)an electron

29. 29  β + decay

30. 30  Nuclei energy levels change, which correspond to different configurations of nucleons within a nucleus  Excited states of a nucleus, nucleons are farther apart, binding energy is less, but the total energy of a nucleus is less than the ground state  When the nucleus makes a transition to a lower energy level, it emits a gamma ray photon

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