Radiation

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Radiation
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• Strong force in nucleus causes protons and
  neutrons to be attracted to each other

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Radiation energy or particles released from the
nucleus of an unstable nucleus. Radiation is
usually a result of an improper ratio of protons
to neutrons in the nucleus.
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All elements larger than Bi (83) are
radioactive What causes radiation?
Nucleus too large (strong force becomes weak)
Wrong number of neutrons to protons in nucleus
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Three Major Types of Radiation Alpha Particle
- Beta Particle - Gamma Ray (not a particle) -
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Alpha particle (a) 2 protons and 2 neutrons
having a charge of 2. The alpha particle
resembles a helium nucleus expelled from the
nucleus. The alpha particle can only travel a
few centimeters through the air.
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Beta particle (ß) an electron like particle
emitted when a neutron changes into a proton.
Beta particles are more penetrating than the
alpha particle.
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Gamma ray (?) very high energy wave or ray
emitted from the nucleus. Gamma rays can
penetrate several feet of concrete or several
inches of lead.
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Radioactivity causes ionization as it passes
through matter. The ions can be detected using
photographic film, a Geiger counter, a cloud
chamber, or a bubble chamber
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Transmutation is the change from one element to
another through nuclear decay
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Fission is the splitting of a large nucleus to
produce two smaller nuclei, neutrons, and lots of
energy
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Fusion the combining of two smaller nuclei to
make a larger nucleus. Powers stars like our sun
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Chain Reaction is an ongoing series of fission
reactions
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Critical Mass is the smallest amount of
fissionable material for a chain reaction
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• Medical Uses for radiation
• Tracer used to find or track molecules in an
  organism
• Cancer treatment control the growth of cancer
  cells.
• Tumor destruction

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• Radiation can also be used to kill bacteria
• Sterilize food
• hospital equipment
• Farm produce

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Everything living (and food) is also radioactive.
Radiation also comes from space. Some comes
from the Sun, some comes from the ground below
you as radon gas. All of this radioactivity is
called the background radiation.
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Half-life is the time taken for half of the
radioactive nuclei to decay. Half-Life is used
to measure the Age of rocks and archaeological
specimens.
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All living things take in carbon-14. The amount
of carbon-14 remaining after death can be used to
determine the age of something once living. This
is called carbon dating.
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To determine the number of half-lives
Original Amount 2 until you get the final
amount. Count the number of times you divided
Convert fraction to half-life
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What to do when asked How much remains.
Original amount 2 for each half-life
Original amount x the fraction equal to the
number of half-lives
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What to do when asked What is the original
amount.
Final amount X 2 for each half-life
Final amount the fraction equal to the number
of half-lives
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How old is the . Or how long will it take..
Length of one half-life X the number of
half-lives
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The half-life of carbon-14 is 5,730
years.Question - If a specimen sample had an
amount of carbon-14 which was 25 of the amount
in today's environment, how old would the sample
be?
The sample is 2 x 5730 11,460 years old.
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The half-life of a given isotope is 10 years.
What mass of a 100 gram sample will remain after
20 years?
1 half-life (10 years) 100 2 50 g 2
half-lives (10 10 years) 50 2 25 g
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What fraction of a sample of Polonium-210
(half-life 138 days) will remain after 552 days?
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What is the approximate age of dead wood whose
level of radioactivity is ¼ that of living wood?
Assume the half-life of 5730 years.
Ans. 11460 years
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The half-life of Thorium is 18.72 days. How many
days are required for three-fourths of a given
amount to decay?
Ans. 37.44 days
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The half-life of a sample is 6.75 hours. How
much a given amount remains after 33.75 hours?
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After 4860 years, how much of an original 0.250
grams of the sample remains? The half-life is
1620 years.
Ans. 0.03125 grams
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Assuming the half-life of carbon is 5730 years,
the skeleton is 17190 years old. How many
half-lives have occurred?
Ans. 3 half-lives