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Nuclear Chemistry

Nuclear Chemistry. Law of conservation of matter…. …states that matter cannot be created nor destroyed through ordinary chemical means Nuclear reactions are not ordinary chemical means A nucleus can change identity during nuclear reactions. Types of nuclear reactions. Alpha decay

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Nuclear Chemistry

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  1. Nuclear Chemistry

  2. Law of conservation of matter… • …states that matter cannot be created nor destroyed through ordinary chemical means • Nuclear reactions are not ordinary chemical means • A nucleus can change identity during nuclear reactions

  3. Types of nuclear reactions • Alpha decay • Beta decay • Gamma decay • Electron capture • Positron emission

  4. Alpha decay • Involves the production of a helium nucleus • 4He • Ex: 210Po  206Pb + 4He 2 2 84 82

  5. Beta decay • A neutron turns into an proton and ejects an electron from the nucleus • 0e • Ex: 14C 14N + 0e -1 7 6 -1

  6. Positron emission • A neutron turns into a proton and is ejected from the neucleus • The same size as an electron • 0e • Ex: 38K  38Ar + 0e 1 19 18 1

  7. Electron Capture • An electron is captured by the nucleus, bonds with a proton, and forms a neutron • The same size as an electron • 0e • Ex: 106Ag + 0e  106Pd -1 -1 47 46

  8. Gamma Emission • Can accompany any nuclear reaction • Electromagnetic radiation • No mass or charge • 0ƴ 0

  9. Nuclear Fusion • Two smaller nuclei fuse together to form a larger, heavier nucleus • Requires temps of 100,000°C or higher to occur • Occurs in stars

  10. Nuclear Fission • One large nucleus decays and forms two or more smaller nuclei • Occurs in nuclear power plants

  11. Half-Life • The amount of time for ½ of a radioactive substance to decay into a stable substance • Examples: • Carbon-14: 5730 years • Tritium: 12.32 years • Polonium-218: 3.0 min

  12. Half-life calculations • Amount remaining= original amount x 1/2n • Where n is the number of half lives

  13. Phosphorus-32 has a half-life of 14.3 days. How many milligrams of phosphorus-32 remain after 57.2 days if you start with 4.0 mg of the isotope? # of half-lives = 57.2/ 14.3= 4 half-lives Amount left= 4.0 x ½4= 4.0 x ½ x ½ x ½ x ½ = 0.25 mg

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