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It’s better to have a half-life than no life!

It’s better to have a half-life than no life!. Radioactive Decay. What does it mean to be radioactive?. Atoms that are radioactive have nuclei that spontaneously decompose to form a different nuclei and produce one or more particles These particles can be any of the following

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It’s better to have a half-life than no life!

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  1. It’s better to have a half-life than no life! Radioactive Decay

  2. What does it mean to be radioactive? • Atoms that are radioactive have nuclei that spontaneously decompose to form a different nuclei and produce one or more particles • These particles can be any of the following • Alpha particle (42He) • Beta particle (0-1e) • Gamma particle (00γ) • Positron (01e) • Cosmic rays

  3. Radioactive (cont’d) • Atoms that are radioactive have a neutron/proton ratio much greater than 1 • Radioactivity can be detected by a Geiger counter

  4. How do we measure decay? • The term “half-life” is used to time radioactive decay • Half-life means the time it takes for half of a sample to decay. • After one half-life ½ of the nuclei have decayed to different nuclei • After two half-lives ¾ of the nuclei have decayed to different nuclei • 14C = 5.73x103yr 238U = 4.46x109yr

  5. Nuclear Reactions? • A nuclear reaction details how nuclei are changed through the emission (radioactive decay) or absorption (nuclear transformation) of alpha, beta, and gamma particles • Equations are balanced by making sure the sums of the atomic numbers and mass numbers on both sides of the equation are equal

  6. Radioactive Decay • Alpha, beta, and gamma particles are emitted from radioactive nuclei • Alpha particle production • EX: 22288Ra  42He + 21886Rn • Beta particle production • EX: 23490Th  23491Pa + 0-1e • Gamma ray emission (usually accompanies alpha and betaparticles) • EX: 23892U  42He + 23490Th + 00γ

  7. Nuclear Transformation • Heavier elements are made from lighter ones by absorption of alpha particles, beta particles, or smaller nuclei • EX: 147N + 42He  178O + 11H • EX: 2713Al + 42He  3015P + 10n

  8. Try These! • Find the missing particle: • ? + 10n 24997Bk + 0-1e • 2010Ne + ? 2412Mg + 00γ • Write the balanced nuclear equation for the following radioactive decays: (a) beta decay of nickel-63; (b) alpha decay of gold-185.

  9. What use is radioactivity? • Medicine – radioactive materials are used as tracers in the body • Energy sources – energy can be obtained through two nuclear processes • Fission: a nucleus divides into smaller fragments • Fusion: nuclei combine to form a larger nucleus

  10. Fission • Splitting nuclei releases large quantities of energy • Harnessed in nuclear power plants • Reaction is controlled by 2 methods • Neutron moderation: reduces speed of neutrons • Neutron absorption: decreases number of neutrons

  11. What happens in a reactor?

  12. So what is Fusion? • Fusion is much better than fission • Fuels are cheaper • Products are not radioactive • Unfortunately it takes a high temperature for fusion to occur • Fusion is what produces the energy for the sun.

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