Intro to Nuclear Chemistry

1. Intro to NuclearChemistry http://www.chem.orst.edu/graduate/pics/Reactor.jpg

2. How does a nuclear reactor work? http://www.lanl.gov/science/1663/images/reactor.jpg

3. How does a small mass contained in this bomb cause…… • Nuclear Bomb of 1945 known as “fat man” http://www.travisairmuseum.org/assets/images/fatman.jpg

4. …this huge nuclear explosion? http://library.thinkquest.org/06aug/01200/Graphics/705px-Nuclear_fireball.jpg

5. Is there radon in your basement? http://a.abcnews.com/images/Blotter/abc_1radon_ad_070625_ssh.jpg

6. Notation

7. NUCLEAR CHEMISTRY • Deal with the nucleus of the atom. • Inside the nucleus there are 2 type of subatomic particles. They are called NUCLEONS = Protons and neutrons • The nucleons are bound together by a strongforce called binding force.

8. Isotopes • Atoms of a given element with: same #protons but different # neutrons

9. H H H http://education.jlab.org/glossary/isotope.html

10. Isotopes of Carbon

11. Radioactive Isotopes • Isotopes of certain unstable elements that spontaneously emit particles and energy from the nucleus. • Henri Beckerel 1896 accidentally observed radioactivity of uranium salts that were fogging photographic film. • His associates were Marie and Pierre Curie.

12. Marie Curie: born 1867, in Poland as Maria Sklodowska • Lived in France • 1898 discovered the elements polonium and radium. http://www.radiochemistry.org/nuclearmedicine/pioneers/images/mariecurie.jpg

13. Marie Curie a Pioneer of Radioactivity • Winner of 1903 Nobel Prize for Physics with Henri Becquerel and her husband, Pierre Curie. • Winner of the sole 1911 Nobel Prize for Chemistry.

14. RADIOACTIVITY • Emission of rays and particles from unstable nuclei. • When a nucleus is emitting rays or particles it is said that is DECAYING or is disintegrating.

15. Stability of nuclei: • Depend on the ratio between the neutrons and protons. Too many or too few neutrons lead to an unstable nucleus. All elements with more than 83 protons are unstable.

16. Types ofNatural Decay

17. NATURAL DECAY There are 4 types of naturally occurring disintegration or decay. USE TABLE O! • Alpha ( a ) decay - Nucleus of He • Beta ( b ) decay - Electrons • Gamma (g ) radiation - Energy • Positron emission

19. SeparationAlphaBetaGamma.MOV Separation of Radiation

23. Transmutation • When the nucleus of one element is changed into the nucleus of another element. IT CAN ONLY HAPPEN IN A NUCLEAR REACTION!!!

24. Nuclear Reactions • The chemical properties of the nucleus are independent of the state of chemical combination of the atom. • In writing nuclear equations we are not concerned with the chemical form of the atom in which the nucleus resides. • It makes no difference if the atom is as an element or a compound. • Mass and charges MUST BE BALANCED!!!

25. Alpha Decay Emission of alphaparticlesa : • helium nuclei • two protons and two neutrons • charge +2e  • can travel a few inches through air • can be stopped by a sheet of paper, clothing.

26. Alpha Decay Uranium Thorium

27. Alpha Decay http://education.jlab.org/glossary/alphadecay.gif

28. 238 92 234 90 4 2 4 2 He U Th He +  Alpha Decay: Loss of an -particle (a helium nucleus)

29. Alpha Decay • Mass changes by 4 • The remaining fragment has 2 less protons • Alpha radiation is the less penetrating of all the nuclear radiation (it is the most massive one!)

30. Alpha decay: • When a nucleus emits alpha particles. • * Atomic number decreases by 2. • * Mass number decreases by 4. • * Neutrons decrease by 2.

31. 131 53 131 54 0 −1 0 −1 0 −1 e I Xe e  +  or Beta Decay: Loss of a -particle (a high energy electron)

32. Beta Decay • Beta particles b: electrons ejected from the nucleus when neutrons decay ( n -> p+ +b- ) • Beta particles have the same charge and mass as "normal" electrons.

33. Beta Decay • Beta particles b: electrons ejected from the nucleus when neutrons decay n -> p+ +b- • Beta particles have the same charge and mass as "normal" electrons. • Can be stopped by aluminum foil or a block of wood.

34. Beta Decay • When a neutron becomes a proton and emits an electron. • * Atomic Number or number of protons increases by 1 • * Number of neutrons decreases by one. • * Mass number remains the same.

35. Beta Decay

36. Beta Decay Thorium Protactinium

37. Beta Decay • Involves the conversion of a neutron in the nucleus into a proton and an electron. • Beta radiation has high energies, can travel up to 300 cm in air. • Can penetrate the skin

38. Beta decay • Write the reaction of decay for C-14

39. Positron Emission • When a proton changes to a neutron emits a positron. • *Atomic number (number of protons)decreases by 1 • *Number of neutrons increase by 1. • *Mass number remains same

40. 0 0  Gamma Emission: Loss of a -ray (high-energy radiation that almost always accompanies the loss of a nuclear particle)

41. Gamma Decay • Gamma radiation g : electromagnetic energy that is released.  • Gamma rays are electromagnetic waves. • They have no mass. • Gamma radiation has no charge. • Most Penetrating, can be stopped by 1m thick concrete or a several cm thick sheet of lead.

42. 3 Main Types of Radioactive Decay • Alpha a • Betab • Gamma g

43. Examples of RadioactiveDecay Alpha Decay Po  Pb + He Beta Decay p n + e n  p + e C  N + e Gamma Decay Ni  Ni + g (excited nucleus)

46. Nuclear Stability • Depends on the neutron to proton ratio.

47. Band of Stability Number of Neutrons, (N) Number of Protons (Z)

48. What happens to an unstable nucleus? • They will undergo decay • The type of decay depends on the reason for the instability

49. What type of decay will happen if the nucleus contains too many neutrons? • Beta Decay

50. Example: 14 14 0 C  N + e In N-14 the ratio of neutrons to protons is 1:1 6 -1 7