Marie Curie: Pioneer of Radiation Research

1. Chapter 25

2. Marie Curie Marie Curie was a Polish scientist whose research led to many discoveries about radiation and radioactive elements. In 1903, she won the Nobel Prize in physics. In 1911, she won the Nobel Prize in chemistry. Her discoveries are essential to understanding and using newly discovered radioactive elements. In 1934, she died from leukemia caused by her long-term exposure to radiation.

3. Chapter 25.1 – Nuclear Radiation • Radiation is the penetrating rays and particles given off by a radioactive source • Radioisotopes are atoms that have a unstable nucleus and can gain stability by undergoing a change during a reaction • Radioactive Decay is when an unstable nucleus releases energy by emitting radiation

5. Even though the nucleus of an atom is so small, the two strongest forces in nature are forced against each other • When the balance is broken, an enormous amount of radioactive energy is released

6. Types of Radiation • There are three main types of nuclear radiation: • Alpha radiation • Beta radiation • Gamma radiation

9. Particle Charge Symbol Penetration  (alpha) +2 4 He 2 LOW, Shielded by paper or clothes  (beta) -1   0 e -1 MODERATE, Shielded by metal or wood  (gamma) 0  VERY HIGH, Shielded by lead or concrete Summary of all three particles

10. Reminder… Mass # = # of protons + # of neutrons X Element Symbol A Z Atomic # = # of protons

12. Alpha Decay Cannot penetrate through paper, but as the ability to ionize molecules • Can cause cancer if inhaled • Can be accelerated in an electric or magnetic field • Uranium-233 undergoes alpha decay 233 229 4 U + Th He 92 90 2

13. Alpha Decay Practice • If a sample of 224-Pa undergoes alpha decay, what is/are the product(s)? Answer = 220-Ac

15. Beta Decay Can penetrate skin and can ionize atoms Can cause cancer Can be accelerated in an electric or magnetic field Copper-66 undergoes beta decay 66 66 0 Cu + Zn e 29 30 -1

16. Beta Decay Practice • If a sample of 234-Pa undergoes beta decay, what is/are the product(s)? Answer = 234-U

17. Similar to high-energy X-Rays • Can pass through thick metal • Does not have high ionizing power • May cause burns, cancer, or genetic mutations

18. Chapter 25.2 – Nuclear Transformations How Carbon-14 Dating Works? An archaeologists finds a piece of a wooden tool used 5,000 years ago. Another finds a child mummy high in the Andes that lived more than 2,000 years ago. How do scientists know how old an object or human remains are? RADIOACTIVITY

19. Carbon-14 Dating • Carbon-14 dating is a way of determining the age of biological artifacts up to about 50,000 years old • It can date things such as bone, cloth, wood, and plant fibers

20. How Carbon-14 is Made • (1. ) Cosmic rays enter the earth’s atmosphere every day • (2.) Cosmic rays collide with atoms in the atmosphere creating neutrons • (3.) Neutrons collide with N2 to make C-14

21. Carbon-14 in Living Things • (4.) The C-14 combines with O2to form CO2 • (5.) Plants then absorb the C-14 during photosynthesis • (6.) Animals and people eat plants and take in C-14 • (7.) C-14 atoms are decaying, but are being replaced by new C-14 at a constant rate

22. Dating a Fossil • As soon as a living organism dies, it stops taking in new carbon • Carbon-14 is radioactive and has a half-life of 5,730 years • By looking at the ratio of C-12 to C-14, it is possible to determine the age of a formerly living thing

24. Half-Life • After each half-life, half of the existing radioactive atoms have decayed into atoms of a new element Time = Ln( ) · H Final Amount Initial Amount -0.693

25. Half-Life Practice • If you have 20 grams of 224-Pa and the isotope has a half-life of 1 second, how much is left after 4 seconds? Answer = 1.25 grams If you have 20 grams of 234-Pa and the isotope has a half-life of 7 hours, how long do you have to wait until you have only 5 grams? Answer = 2 half-lives or 14 hours

26. Radioisotopes • The use of various radioisotopes allows the dating of biological and geological samples • However, radioisotope dating may not work so well in the future • Anything that dies after the 1940s when nuclear bombs, nuclear reactors, and open-air nuclear tests began will be harder to date

27. Chapter 25.3 – Fission and Fusion of Atomic Nuclei • Fission is a heavy nucleus splitting into two lighter nuclei • Uranium-235 and Plutonium-239 are the only fissionable isotopes • Nuclear fission can release an enormous amount of energy • 1 kg of Uranium  20,000 tons of dynamite

28. Chain Reaction • In a chain reaction, some neutrons react with other fissionable atoms producing more neutrons which will react with more fissionable atoms….

29. Fusion • Fusion is two nuclei combining to produce one nucleus of greater mass • Fusion reactions release much more energy than fission reactions, but only occur at temperatures higher than 40,000,000°C • Therefore, high energy is required for fusion reactions 2 2 4 H + H He + energy 1 1 2

30. Chapter 25.4 – Radiation in Your Life • A common household smoke detector uses the radiation from a radioisotope (Americium) in order to operate • The radiation from Americium ionizes the nitrogen and oxygen in smoke-free air allowing a current to flow through • When smoke particles get in the way, they are ionized instead and the drop in current causes the alarm to sound • Ionizing Radiation is any radiation emitted by radioisotopes

31. Geiger Counter • Uses a gas-filled metal tube to detect radiation • When radiation penetrates a thin window at one end of the tube, the gas inside the tube becomes ionized • Every time a Geiger tube is exposed to radiation, the current flows and causes audible clicks from a speaker • Can detect alpha, beta, and gamma radiation

32. Scintillation Counter • Uses a phosphor-coated surface to detect radiation • Radiation strikes the phosphor surface and produces bright flashes of light (scintillations) • The number of flashes are detected electronically • The information is converted into electronic pulses, measured, and recorded

33. Film Badge • Consists of several layers of photographic film covered with black lightproof paper • Important for people working near radiation • The film is removed and developed frequently to measure the amount of radiation exposure • Records are kept to monitor the degree of exposure to radiation • This does not protect a person from radiation

34. Using Radiation • Although radiation can be harmful, it can also be used safely • Neutron Activation Analysis is a procedure used to detect amounts of elements in samples • Used in museums to detect art forgeries, crime labs to analyze gun powder residues, agriculture to test the effects of herbicides, pesticides, and fertilizers

35. Radioisotopes in Medicine • Iodine –131 is used to detect thyroid problems • Technetium-99 is used to detect brain tumors and liver disorders • Phosphorus-32 is used to detect skin cancer

36. Radiation Treatment • Cancer is a disease in which abnormal cells in the body are produced at a rate far beyond the rate of normal cells • A mass of cancerous tissue is called a tumor • Often times, radiation therapy is used to treat cancer because the cancer cells are more susceptible to damage by radiation than healthy cells • However, normal cells are also killed during the radiation treatment which makes people weak