Chapter 4 & 25 Nuclear Chemistry

1. Chapter 4 & 25 Nuclear Chemistry • Chapter 4 & 25 Nuclear Chemistry

2. 4.4 Unstable Nuclei and Radioactive Decay • Chemical reactions involve only electrons, NOT the nucleus. • Protons determine the identity of an atom. • Change the protons, it is a different atom!!

3. 4.4 Unstable Nuclei and Radioactive Decay • Nuclear Reactions- reactions which involve a change in an atom’s nucleus

4. Radioactivity- substances spontaneously emit radiation

5. Radiation- rays and particles emitted by the radioactive material • By emitting radiation, atoms of one element can change into atoms of another element.

6. Radioactive atoms • Emit radiation because their nuclei are unstable. • Radioactive decay-a spontaneous process in which unstable nuclei lose energy by emitting radiation

7. Unstable radioactive atoms undergo radioactive decay until they form stable non radioactive atoms of a different element.

8. History of Radioactivity • http://www.adaptivecurriculum.com/proxy/AC/TPlayer/v0.0.9/actplayer.jsp#

9. Chapter 25: Nuclear Chemistry25.1 Nuclear Radiation • 1895- William Roentgen; discovered x-rays (form of high-energy electromagnetic radiation) • rays caused photographic plates to darken

10. He took “pictures” of his wife’s hand. • rays caused photographic plates to darken • In 1901 Röntgen was awarded the very first Nobel Prize in Physics.

11. Henri Becquerel • 1896 - studied minerals that emit light after being exposed to sunlight- called phosphorescence. • He wondered if they also emitted X-rays.

12. Accidentally, he discovered uranium emitted radiation without an external source of energy such as the sun. Becquerel had discovered radioactivity, the spontaneous emission of radiation by a material.

13. Later, Becquerel demonstrated that the radiation shared certain characteristics with X rays but, unlike X rays, radiation could be deflected by a magnetic field and therefore must consist of charged particles. • For his discovery of radioactivity, Becquerel was awarded the 1903 Nobel Prize for physics.

14. Marie Curie and Pierre Curie took Becquerel’s mineral and isolated components; found that rays were being emitted by Uranium they called this process radioactivity Marie discovered that the uranium nucleus is radioactive Becquerel & Curies shared Nobel prize for their work The Curies

15. 1898 - Marie and Pierre Curie – isolated the elements that were emitting the rays. • polonium, and radium

16. Rate of radioactive emission of charged particles from elements could be measured and compared. • In addition, she found that there was a decrease in the rate of radioactive emissions over time and that this decrease could be calculated and predicted. • But perhaps Marie Curie's greatest and most unique achievement was her realization that radiation is an atomic property of matter.

17. Nobel Prize in Physics 1903 – was shared; Curies and Becquerel for work in radioactivity • Nobel Prize in Chemistry 1911 – Marie Curie for her work with the elements Polonium and Radium.

18. 3 Types of Radiation • 1800’s Scientistsdirected radiation between 2 electrically charged plates and found there were 3 different types; some deflected to the negative, some to the positive, and some were not deflected at all.

19. Types of Radiation • Radioisotopes- isotopes of atoms with unstable nuclei • C-14 is a radioisotope of C-12 • Most common types of radiation are alpha, beta, and gamma rays

20. Experiment

21. Alpha Particle • an alpha particle (we use the symbol α) is positive • Alpha Radiation- radiation deflected toward the negatively charged plate

22. Alpha particle • contains 2 protons • 2 neutrons • and has a 2+ charge • Has a mass number of 4

24. Alpha Radiation

25. Positive charge is why it is attracted to negative plate • Equivalent to helium-4 nucleus • Ex:

26. Beta Radiation • a beta particle (symbol β) is negative • Beta Radiation- radiation that was deflected towards the positively charged plate • Beta Particles- radiation consisting of fast moving electrons

27. Beta particles consist of an electron with a 1- charge • Ex:

28. Beta Particles A neutron becomes a proton and an electron. The electron leaves the atom at high speed.

29. What blocks these rays!

30. Gamma Radiation • a gamma ray (symbol γ) is neutral • Gamma Rays-high-energy radiation that possesses no mass and no charge • Usually accompany alpha and beta radiation

31. Accounts for most of the energy lost during radioactive decay • Gamma rays cannot result in the formation of a new atom • Ex:

32. What blocks these rays!

33. Practice worksheet

34. 25.4 Fission and Fusion of Atomic Nuclei • Nuclear Fission- the splitting of a nucleus into fragments; accompanied by a very large release of energy

35. During fission, a neutron collides into an unstable nucleus causing a chain reaction

36. The neutrons released can cause more fissions, which releases more neutrons causing more fissions and so on.

37. Chain reaction – self-sustaining process in which one reaction initiates the next. • Critical mass – a sample that is massive enough to sustain a chain reaction. • More than a critical mass can generate a nuclear explosion.

38. Nuclear Fission Reaction • Heavier isotopes is broken down into lighter isotopes

39. Uses of Fission • Nuclear Power plants • Building of the A-bomb

40. Fusion • Nuclear Fusion- the combining of atomic nuclei; capable of releasing large amounts of energy • Ex.: Sun powered by a series of fusion reactions • high amount of energy is required to create reaction

41. Fusion Equation

42. 25.5 Applications and Effects of Nuclear Reactions • Ionizing radiation - radiation energetic enough to ionize (damage) matter with which it collides. • Detected by Geiger counters

44. Uses of Radiation • Radiotracer - radioisotope that emits non-ionizing radiation and is used to signal the presence of an element or specific substance. • a. analyze reactions • b. detect diseases • c. PET scans

45. PET scan (positron emission tomography)

46. Medical Uses of Radiation • Diagnostic: Radiotracers such as technitium-99 can be injected in the blood stream and then tracked through the body to see if organs are functioning properly; also can help diagnose cancer (PET scan)

47. Therapy: Radiation treatments can kill the cancer cells in cancer patients

48. Commercial applications • Smoke detectors: have a tiny mass of americium-241, which is a source of alpha radiation • Rifle sights: tritium is used with phosphor to increase nighttime firing accuracy

49. Exit signs: luminescence is due to a small amount of radioactivity • Food irradiation:exposing food to ionizing radiation to destroy microorganisms, bacteria, viruses, and insects

50. X-Rays • X-rays and gamma rays – high-energy electromagnetic radiation that is extremely penetrating and damaging to living tissue. • Blocked by lead and concrete.