History and Introduction ([email protected]) Why Radiochemistry IGERT program at Hunter...
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Transcript of History and Introduction ([email protected]) Why Radiochemistry IGERT program at Hunter...
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
Radioactivity
Radioactivity is emitted by atoms which are unstable and undergo radioactive decay
Many elements in the periodic table are naturally radioactiveother radioactive elements can be produced
Doing chemistry with radioactive elements is called “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.
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.
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.
Brief history of radiochemistry
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.
1898 – Marie and Pierre Curie
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”
atomic radius ~ 100 pm = 1 x 10-10 m
nuclear radius ~ 5 x 10-3 pm = 5 x 10-15 m
Rutherford’s Model of the Atom
Radioactivity: reactions of the nucleus of the atom
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)
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: 00
-01
147
146 βNC
Parent nuclideDaughter nuclide
Radiation
Radioactivity: reactions of the nucleus of the atom
Half-lives (t½): — time required for ½ of the material to decay
0 20 40 60 80 1000
200
400
600
800
1000
N1i
N2i
N3i
M1j
M2j
M3j
,,,,,i i i j j jtime (minutes)
num
ber
of n
ucle
i rem
aini
ng
t½ = 15 m t½ = 30 m
t½ = 50 m
½
0.693 t
tt 0N N e
Radioactive Decay
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
Electromagnetic Spectrum
We try to “harness” ionizing radiation for useful purposes, specifically diagnosis of disease (imaging) and therapy of disease
- 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
Types of Ionizing Radiation
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).
Types of Ionizing Radiation
Betaβ+ or
positronβ- or
electron
Gammax-ray or
photon
Alpha or 242α
242He
Applications of Radiation
Ionization Technology. U.S. Environmental Protection Agency. http://www.epa.gov/rpdweb00/sources/smoke_ion.html (accessed Jun 8, 2011).
Smoke
Alarm
CurrentDisrupte
d
• Nuclear Power• Nuclear Medicine• Nuclear Forensics• Drug design• Smoke Detectors