• Nuclear reactions change an atom’s nucleus.
• 3 Types of radiation are produced from
nuclear reactions: alpha, beta & gamma.
–Gamma: no charge
• Strong nuclear force: force that holds
the protons together in the nucleus
• Neutrons add a strong nuclear force
to a nucleus, which keeps the protons
from breaking the nucleus apart.
• All nuclei with atomic numbers >83
• Beyond 20 protons, nuclei need many
more neutrons than protons to be
• Nuclei can become unstable if there
are too many or too few neutrons.
• Isotopes that are much heavier or
much lighter than the most common
isotope are likely to be radioactive.
• An alpha (α) particle has 2 neutrons & 2
protons and is identical to a He-4 nucleus.
• a neutron changes into a proton &
• The proton stays in the nucleus & the
electron/beta particle is propelled out of
• Beta particle = electron
• Gamma radiation has no particles.
• Most dangerous type of radiation
• Emitted from the nuclear bomb
• When certain elements are struck with
neutrons, the nucleus can split into smaller
– Only occurs in Uranium-235 & Plutonium-239
– Creates a chain reaction that releases an
immense amount of energy
• ~2 lbs of U-235 creates as much energy as
20,000 tons of dynamite
– Nuclear bombs use fission
– Nuclear Power Plants use fission to heat water
• When 2 or more atoms combine to create one atom
• Occurs in stars, like our sun
– Hydrogen atoms fuse to make helium atoms
– When stars run out of hydrogen, they start to die
• Creates more energy than fission reactions
• Extremely high temperatures are needed to create
a fusion reaction
– We have not been able to attain temperatures
hot enough for us to use nuclear fusion as a
power source on Earth
• Every radioactive sample decays at a certain rate
• A half-life is the time required for half of the
atoms in the sample to decay into products
– Half-lives can range from fractions of a second
to billions of years
– Half-lives of:
• Radon-222: 3.8 days
• Carbon-14: 5730 years
• Uranium-235: 700,000,000 years
amount _ of _ time _ elapsed
length _ of _ halflife
number _ of _ halflives
• The half-life of Carbon-14 is 5730 years.
How many half-lives elapse after 17,190
• How many grams of C-14 is left after 3 halflives if it started off with 100 grams?
• Starting with 80 grams, how many half-lives
have elapsed if you end with 5 grams?
• What is the half-life of a 100 g sample of N16 that decays to 12.5 g in 21.6 seconds?
• If an 800 g sample of technetium-99 decays
to 100 g in 639,000 years, what is its halflife?
• A 208 g sample of sodium-24 decays to 13 g
of sodium-24 within 60 hours. What is the
half-life of this isotope?
• The half-life of Au-198 is 2.7 days. How
much of a 300g sample will be left after
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