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Chemistry 25.2

Chemistry 25.2. 25.2. Nuclear Transformations. Radon-222 is a radioactive isotope that is present naturally in the soil in some areas. It has a constant rate of decay. You will learn about decay rates of radioactive substances. 25.2. Nuclear Stability and Decay. Nuclear Stability and Decay

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Chemistry 25.2

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  1. Chemistry 25.2

  2. 25.2 Nuclear Transformations • Radon-222 is a radioactive isotope that is present naturally in the soil in some areas. It has a constant rate of decay. You will learn about decay rates of radioactive substances.

  3. 25.2 Nuclear Stability and Decay • Nuclear Stability and Decay • What determines the type of decay a radioisotope undergoes?

  4. 25.2 Nuclear Stability and Decay • The nuclear force is an attractive force that acts between all nuclear particles that are extremely close together, such as protons and neutrons in a nucleus • At these short distances, the nuclear force dominates over electromagnetic repulsions and hold the nucleus together.

  5. 25.2 Nuclear Stability and Decay • More than 1,500 different nuclei are known. Of those, only 264 are stable and do not decay or change with time. These nuclei are in a region called the band of stability.

  6. 25.2 Nuclear Stability and Decay

  7. 25.2 Nuclear Stability and Decay • The neutron-to-proton ratio determines the type of decay that occurs. • A positron is a particle with the mass of an electron but a positive charge. During positron emission, a proton changes to a neutron.

  8. 25.2 Nuclear Stability and Decay

  9. 25.2 Half-Life • Half-Life • How much of a sample of a radioisotope remains after each half-life?

  10. 25.2 Half-Life • A half-life (t1/2) is the time required for one-half of the nuclei of a radioisotope sample to decay to products. • After each half-life, half of the existing radioactive atoms have decayed into atoms of a new element.

  11. 25.2 Half-Life

  12. 25.2 Half-Life

  13. Half-Life • Simulation 30 Simulate the decay of several isotopes.

  14. 25.2 Half-Life Stable Isotope

  15. 25.2 Half-Life • The ratio of Carbon-14 to stable carbon in the remains of an organism changes in a predictable way that enables the archaeologist to obtain an estimate of its age.

  16. 25.1

  17. 25.1

  18. 25.1

  19. 25.1

  20. for Sample Problem 25.1 Problem Solving 25.7 Solve Problem 7 with the help of an interactive guided tutorial.

  21. 25.2 Transmutation Reactions • Transmutation Reactions • What are two ways that transmutation can occur?

  22. 25.2 Transmutation Reactions • The conversion of an atom of one element to an atom of another element is called transmutation. • Transmutation can occur by radioactive decay. Transmutation can also occur when particles bombard the nucleus of an atom.

  23. 25.2 Transmutation Reactions • The first artificial transmutation reaction involved bombarding nitrogen gas with alpha particles.

  24. 25.2 Transmutation Reactions • The elements in the periodic table with atomic numbers above 92, the atomic number of uranium, are called the transuranium elements. • All transuranium elements undergo transmutation. • None of the transuranium elements occur in nature, and all of them are radioactive.

  25. 25.2 Transmutation Reactions • Transuranium elements are synthesized in nuclear reactors and nuclear accelerators.

  26. 25.2 Section Quiz. • 25.2.

  27. 25.2 Section Quiz. • 1. During nuclear decay, if the atomic number decreases by one but the mass number is unchanged, the radiation emitted is • a positron. • an alpha particle. • a neutron. • a proton.

  28. 25.2 Section Quiz. • 2. When potassium-40 (atomic number 19) decays into calcium-40 (atomic number 20), the process can be described as • positron emission. • alpha emission. • beta emission. • electron capture.

  29. 25.2 Section Quiz. • 3. If there were 128 grams of radioactive material initially, what mass remains after four half-lives? • 4 grams • 32 grams • 16 grams • 8 grams

  30. 25.2 Section Quiz. • 4. When transmutation occurs, the ________ always changes. • number of electrons • mass number • atomic number • number of neutrons

  31. 25.2 Section Quiz • 5. Transmutation occurs by radioactive decay and also by • extreme heating. • chemical reaction. • high intensity electrical discharge. • particle bombardment of the nucleus.

  32. END OF SHOW

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