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PHYSICAL SCIENCE
sixth edition
Bill W. Tillery
Chapter 13
Nuclear Reactions
Copyright В© The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Radioactive particles
Particle Composition Charge
Alpha
О±
Beta
2 protons and
2 neutrons
2+
stopped by
paper
an electron
1-
stopped by
aluminum
pure energy
0
stopped by
lead
ОІ
Gamma
Оі
Penetration
Relative penetrating abilities of alpha, beta, and gamma
radiation
nucleus
• Proton and neutron called “nucleons”
Atomic number (Z) = number of protons in nucleus
Mass number (A) = number of protons + number of neutrons
= atomic number (Z) + number of neutrons
Isotopes - atoms of the same element (X) with different numbers
of neutrons in their nuclei
Mass Number
Atomic Number
235
92
U
A
ZX
Element Symbol
238
92
U
Origins of Radiation Exposure in the US
Natural background (81%):
Biggest source: Radon-222
Medicine (15%)
•
•
•
•
•
Can’t see it
Can’t smell it
Can’t taste it
Can’t hear it
Can’t feel it
Consumer products (4%)
Radon-222
• Chemically inert, uncharged noble gas
• Produced from decay of uranium-238
• Seeps out of rocks and soil
• Builds up indoors and in mines
• T1/2 is 3.8 days
• Decays by alpha particle emission
• Produces short-lived solid alpha-emitters - Polonium 218
and 214
Zone 1 (red zones)
Highest
Potential
Zone 2 (orange zones) Moderate
Potential
Zone 3 (yellow zones) Low
Potential
Biological Effects of Radiation
Units of Radiation
• Radiation absorbed dose (rad)
• Roentgen equivalent for man (rem)
Devices to measure radiation
• Geiger counter
• Personal dosimeters
Fig. 13.11 Working parts of a Geiger counter
Table 10.1
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