Transcript In a nuclear reaction

NUCLEAR CHEMISTRY
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Isotopes-Review

Isotopes are atoms of the same
element that have the same # of
protons but different # of neutrons or
mass.
Atomic mass
X
Atomic number
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NATURAL RADIOACTIVITY
1- Spontaneous Decay- emit energy without
absorption of energy from an out side source.
2- Elements with atomic # greater then Bi 83 are
unstable and are radioactive.
3- Isotopes that are unstable have an unstable ratio
of protons and neutrons greater then 1:1
3- TRANSMUTATION- changes to the nucleus of an
element
3
TYPES OF EMISSIONS
1- ALPHA DECAY:
-Identified as helium nuclei (2 protons & 2
neutrons)
- Both the mass & charge are balanced.
- Total atomic number of reactants = products
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BETA DECAY
1- Have the same charge and mass as electrons
2- Electrons are ejected at high speeds from
radioactive isotopes.
3- A neutron transformed into a proton with creation
of an electron.
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POSITRON EMISSION
1- Same mass as electrons, but + change (NOT -)
2- When positron electrons meet, they annihilate
each other, producing large amounts of energy.
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GAMMA RAYS
1- High energy electromagnetic waves
2- No mass, not considered particles.
3- Have penetrating abilities similar to X-Rays
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CHARACTERISTCS OF ALPHA, BETA, AND
GAMMA EMISSONS
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HALF-LIFE
1- Radioactive isotopes- decay or breakdown at
different or characteristic rates.
2- Half-life: time interval required for half the sample
to disintegrate
3- EX: iodine-131 100grams half-life = 8 days
-0 days = 100g
-8 days = 50g
-16 days = 25g
- 24 days = 12.5 g
4- FIND HALF-LIFE REFERENCE TABLE N
- IF NOT GIVEN START WITH ZERO TIME!!!
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Nuclear Reactions
1- Nuclear Reaction- change in the nucleus of an
atom with a release of large amounts of energy.
2- Nuclear reactions include:
-Spontaneous transmutation
- artificial transmutation
- fission
- fusion
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Artificial Transmutations
1- Artificial Transmutation: bombarding a stable
atom with particles, nuclei become unstable and
isotopes are formed.
1- Creates unstable
fluorine atom that
immediately decays to
oxygen-17 by releasing
a proton
2- Most artificial transmutations occur in particle
accelerators.
3- Elements on the Periodic Table beyond uranium (92U) are
artificial transmutations.
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FISSION
1- Fission: nuclear reaction in which a heavy, unstable
nucleus is split into 2 mid-size nuclei.
- it releases 1 or more neutrons and a large amount of
energy!
2- Controlled reaction in nuclear power plants-produces great
amounts of energy.
-Uncontrolled reaction= nuclear weapons
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FUSION
1- FUSION: When 2 or more light nuclei combine to form a
single nucleus of greater mass.
- Fusion releases more energy then Fission!!!
- Hydrogen bomb- created by FUSION!!!
- FUSION REACTIONS: high temperatures, over 5 million K
and high pressure!
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1- The mass numbers and atomic numbers in a nuclear
reaction are balance, the total mass of products are less.
2- In a nuclear reaction- the mass lost is converted to
ENERGY!
3- Albert Einstein’s equations E = mc2
-the energy produced is equal to the mass lost
- a tiny fraction of the mass is converted to a large amount
of energy
4- LAW OF CONSERVATION OF MASS-ENERGY- combines
both the law of conservation of mass + the law of
conservation of energy!
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Benefits and Risks of Radioactivity
1- NUCLEAR POWER:
- produces electricity by combustion of fossil fuels
- MAJOR RISK: storage of highly radioactive waste
products- long half-lives
-FISSION- produces electricity at low cost and does not
produce CO2- Greenhouse effect. Fission produces energy
released by uranium-235
-FUSION- produces more energy, Hydrogen is abundant
and products are not radioactive
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Radioactive Dating
1- Useful is determining the age of an object by measuring
the amount of radioactive isotope that remains in a sample.
2- Age of fossils- determined from the ration of C-12 & C-14
contained in the sample.
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Medical Diagnosis and Treatment
1- Isotopes- used for diagnosis of diseases and treatments
- used in diagnosis of heart, lung, liver, spleen, & bone
- Iodine-131 used for Thyroid disorders- short half-life
- Cancer treatments- radiation uses Cobalt-60- emits
gamma rays that destroy tumors
- Overexposure can cause mutations in DNA and destroy
health tissue.
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Radioactive Tracers
1- Used in chemical research.
- Identifies and detects intermediate
products along the reaction pathway of
chemical reactions
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Food Safety & Preservation
-Food irradiation kills insects, mold, &
bacteria that cause illness!
-- Kills salmonella and E-coli bacteria
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Industrial Measurement
-Radiation is used to measure the thickness
and physical dimensions of products
- Used to measure and detect structure flaws
in metal parts
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