nuclear chemistry 1 isotopes-review isotopes are atoms of the same element that have the same # of...

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.

XAtomic mass

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 1:13- TRANSMUTATION- changes to the nucleus of an element

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TYPES OF EMISSIONS1- 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 DECAY1- Have the same charge and mass as electrons2- 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 EMISSION1- 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 RAYS1- High energy electromagnetic waves2- 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-LIFE1- Radioactive isotopes- decay or breakdown at different or characteristic rates.2- Half-life: time interval required for half the sample to disintegrate3- 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 Reactions1- 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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FISSION1- 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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FUSION1- 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 energy4- 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 Dating1- 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 Tracers1- 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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