History and Introduction

1. Why Radiochemistry History and Introduction IGERT program at Hunter College (Lfrances@hunter.cuny.edu)

2. Why Radiochemistry and Why Should I Care About Radiation? • Medical applications Molecular Imaging of disease Single Photon Emission Computed Tomography (SPECT) Positron Emission Tomography (PET) Radiotherapy to treat disease • Energy applications • Environmental applications • National Security

3. Radioactivity Radioactivity is emitted by atoms which are unstable and undergo radioactive decay Many elements in the periodic table are naturally radioactive other radioactive elements can be produced Doing chemistry with radioactive elements is called “radiochemistry”

4. Brief history of radiochemistry In 1895, Röntgen discovered X-rays when he worked with electrons in a cathode ray tube—they penetrated black paper. Röntgen won the Nobel Prize in physics in 1901 for this discovery.

5. Brief history of radiochemistry In 1896, Becquerel discovered radioactivity working with uranium compounds. Images were seen on photographic plates on exposure to the uranium compounds, even in the absence of any light.

6. Brief history of radiochemistry Radiation emitted by the uranium was different from X-rays. It could be deflected by a magnetic field and therefore must consist of charged particles. Becquerel was awarded the1903 Nobel Prize in physics for his discovery of radioactivity.

7. 1898 – Marie and Pierre Curie The term radioactivity was coined by Marie Curie. Working with uranium ore, she and Pierre Curie discovered the radioactive elements polonium (Po) and radium (Ra). The Curies were awarded the 1903 Nobel Prize in physics for their work on radioactivity.

8. 1912 — George de Hevesy Father of the “radiotracer” experiment. 1923: 212Pb to study the absorption and translocation of Pb(NO3)2 in bean plants. Received the Nobel Prize in chemistry in 1943 for his concept of “radiotracers”

9. Radioactivity: reactions of the nucleus of the atom Rutherford’s Model of the Atom atomic radius ~ 100 pm = 1 x 10-10 m nuclear radius ~ 5 x 10-3 pm = 5 x 10-15 m If the atom is the Football Field Then the nucleus is a marble on the 50 yard line

10. Reactions of the nucleus of the atom: Subatomic Particles mass p = mass n = 1840 x mass e- mass alpha particle = mass 2 p + mass 2 n mass alpha particle = 7360 x mass e- (beta particle)

11. Radioactivity: reactions of the nucleus of the atom • Nuclear decay often results in a transmutation reaction which is the process of an atom changing atomic number and becoming a different element • Example: Parent nuclide Radiation Daughter nuclide

12. Radioactivity: reactions of the nucleus of the atom Radioactive Decay Half-lives (t½):— time required for ½ of the material to decay

13. Ionizing Radiation • * Radioactive decay emits ionizing radiation • * Ionizing radiation consists of particles or waves with enough energy to remove electrons from surrounding atoms or molecules IonizingRadiation Non-IonizingRadiation We try to “harness” ionizing radiation for useful purposes, specifically diagnosis of disease (imaging) and therapy of disease Electromagnetic Spectrum

14. Types of Ionizing Radiation  - alpha particle—He2+ nucleus ---beta particle—e- ejected by nucleus +--positron—e+ ejected by nucleus • Undergoes annihilation to emit two 0.511 MeV photons at 180o --gamma ray—photon emitted by nucleus

15. Types of Ionizing Radiation • Alpha • or • Beta • β+ or positron • β- or electron • Gamma • x-ray or photon Ionizing Radiation Fact Book, 2007. U.S. Environmental Protection Agency. http://www.epa.gov/radiation/docs/402-f-06-061.pdf (accessed Jun 7, 2011).

16. Applications of Radiation • Nuclear Power • Nuclear Medicine • Nuclear Forensics • Drug design • Smoke Detectors Alarm Current Disrupted Smoke Ionization Technology. U.S. Environmental Protection Agency. http://www.epa.gov/rpdweb00/sources/smoke_ion.html (accessed Jun 8, 2011).