Nucleons – protons and neutraons Nuclide – an atom Helium has 4 amu , 2 protons

1. Nucleons – protons and neutraons • Nuclide – an atom Helium has 4 amu, 2 protons 2 protons (2 x 1.007276) = 2.014552 amu 2 neutrons (2 x 1.008665) = 2.017330 2 electrons (2 x 0.0005486) = 0.001097 = 4.032979 amu Helium-4 is measured with the mass of 4.002602amu, why is this different?

2. Mass defect • Difference between the mass of an atom and the sum of the masses of its protons, neutrons, and electrons. • Nuclear binding energy: E = mc2 • Difference for He is 0.030377 amu 1 amu = 1.6605 x 10-27kg c = 3 x 108 m/s (speed of light) 0.030377amu x 1.6605 x 10-27kg/1 amu = 5.0441 x 10-29kg

3. E = (5.0441 x 10-29kg)(3x108m/s)2 E = 4.54 x 10-12J Nuclear binding energy – the energy released when a nucleus is formed from nucleons *can help us measure the stability of a nucleus.

4. Binding energy = binding energy per nucleon • The higher the binding energy per nucleon, the more tightly the nucleons are held together. • The higher the binding energy  the more stable the atom is.

5. Nuclear shell model = the nucleons exist in different energy levels, or shells in the nucleus. • Magic numbers – the number of nucleons that represent copleted nuclear energy levels 2,8,20,28,50,82,126 Most stable nuclides

6. Nuclear reaction – rxn. That changes the nucleus of an atom • Transmutation – change in the identity of a nucleus as a result of a change in the number of its protons.

7. Radioactive decay • Becquerel • Spontaneous disintegration of a nucleus into a slightly lighter nucleus, accompanied by emission of particles, electromagnetic radiation, or both. • * all of the nuclides beyond atomic #83 are unstable and thus radioactive.

8. Alpha emission • Two protons and 2 neutrons • Heavy nuclides do this

9. Beta emission • Negative • Neutron/proton ratio is too large • To decrease the # of neutrons, a neutron can be converted into a proton and an electron. • e- is emitted • Antineutrino is emitted as well (nuetral) opposite spin of a neutron,

10. Beta emission • Positive • Unstable because neutron/proton ratio is too small • Need to decrease # of protons • A proton is converted to a neutron.

11. Electron capture • An inner orbital e- is captured by the nucleus of its own atom. • Neutron = 1 proton and 1 electron • Proton + e-  nuetron

12. Gamma emission • High energy electromagnetic waves emitted from a nucleus as it changes from an excited state to a ground energy state. • Gamma rays are produced when nuclear particles undergo transitions in nuclear-energy levels. • Similar to when e- go to different energy leveles and emit light.

13. Usually occurs immediately following other types of decay, when other types of decay leave the nucleus in an excited state

14. Half-life • T1/2 the time required for half the amount of a radioactive nuclide to decay. • Less stable nuclides decay very quickly and have shorter half-lives Ex.

15. Decay series • Series of radioactive nuclides produced by successive radioactive decay until a stable nuclide is reached. • Parent nuclide – the heaviest nuclide of each decay series. • Daughter nuclide – nuclides produced by the decay of the parent nuclides.

16. Radioisotopes in medicine • Radioisotopes – radioactive isotopes. • Diagnostic – helps doctors understand what is happening inside the body. • Therapeutic – treating a medical condition. • Radioisotope-tracerstudies – these isotopes collect in a certain part of the body, physicians can investigate a given part of the body by using an appropriate radioisotope (tracer)

17. https://www.youtube.com/watch?v=QvXHvDCesqg • Nuclear medicine

18. Iodine-123 is used to diagnose problems of the thyroid gland, which is located in the neck. • Measures how fast the thyroid takes in this element. • Physician can determine an overactive or underactive thyroid gland. • Gall bladder

19. Therapeutic radioisotopes – emit radiation that carries sufficient energy to destroy living tissue. • Chemotherapy • Radioiodine – collects in and destroys the cancerous portion of the thyroid gland ---thyroid cancer. • Pg. 529

20. Positron emission tomography (PET) scan – emits positrons, same mass as beta particles (e-). • + charge • When a positron encounters an electron, both particles are destroyed (this is why its called antimatter) • And two gamma rays are emitted

21. PET detects these gamma-ray pairs and determine where they originated • The radioisotope tracer attaches to sugar molecules • Physicians can see these sugar molecules in the body. • Since cancer grows faster than normal cells, more sugar will be seen in these places. • Find cancer without surgery.

22. MRI • Images of soft tissues • Uses radio waves of very low energies and involves no health risks.

23. Nuclear Power • In a nuclear power plant, radioactive elements, such as Uranium are bombarded with neutrons. • The neutrons make the unstable nuclei of uranium split. • The nucleons then hit other atoms and then they split  change reaction. • The splitting releases the energy as heat.

25. There are rods that go down into the chamber that either absorb or release neutrons. • This controls the nuclear fission. • If the nuclear fission gets out of control then there would be too much heat energy and there will be a meltdown. • The heat, heats up water and the water turns to steam which then turns turbines then a generator.

27. https://www.youtube.com/watch?v=_AdA5d_8Hm0 • Tour of nuclear power plant

28. Radioactive waste • underneath Yucca Mountain in the Nevada desert 80 miles from Las Vegas