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Nuclear Radiation

Nuclear Radiation. Nuclear Radiation. Nucleus has protons (+ charge) and neutrons (no charge). Electrons are not in the nucleus and do not influence nuclear processes. Isotopes.

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Nuclear Radiation

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  1. Nuclear Radiation

  2. Nuclear Radiation • Nucleus hasprotons (+ charge) and neutrons (no charge). • Electrons are not in the nucleus and do not influence nuclear processes.

  3. Isotopes • Isotopes: Atoms of the same element (same number of protons) but with different nuclei due to different numbers of neutrons. + + n n n + 1H 3H 2H More massive!

  4. Naming Isotopes – 14N • Isotopes are named by their element name and their mass number. • 14N has 7 protons (because it is nitrogen) and 7 neutrons (7 p + 7 n = 14) • How many p and n in 14C? + + + + + + n n n n n n n n

  5. Why are isotopes important? • Radioactivity depends on neutron/proton ratio. • Big atoms: can be stable if n > p. Lead-206 is stable. It has 82 p and 124 n. Uranium 238 is unstable. It has 92 p and 146 n. • Small atoms: stable when p  n. • Oxygen-16 is stable. It has 8 p and 8 n.

  6. Summarizing Questions Part 1 • Does the number of neutrons have any apparent effect on the name or behavior of an atom? • If your uncle asked you what an isotope is, what would you tell him? Does an atom’s positive or negative charge affect its radioactivity?

  7. What is radiation? • Radiation: High energy particles that come out of the nucleus of some atoms. • A Geiger counter detects these • Each is a quantum (plural quanta)

  8. Alpha Particles • 2 protons + 2 neutrons. • High energy! • Remaining nucleus has less mass. Alpha Polonium-218 p: 84 n: 134 Radon-222 p: 86 n: 136

  9. Beta Particles • An electron leaves the nucleus …but there are no electrons in the nucleus! • A neutron breaks into a proton + an electron …the proton stays behind. • Proton # increases, neutron # decreases. Carbon-14 p: 6 n: 8 Nitrogen-14 p: 7 n: 7 Electron +

  10. Gamma Particles • Gamma particles are pure energy -electromagnetic radiation (like x-rays) • No change in the number of p & n. • Most alpha and beta decay also has gamma.

  11. Check your understanding • Are alpha, beta, or gamma particles radioactive? Is radioactivity like dirt? When radiation gets on you do you become radioactive? • Do you agree with Rob or Maria? • Rob: “An atom is not radioactive - it only emits radiation for a short time.” • Maria: “But radiation comes from the atoms so they must be radioactive.”

  12. Practice 1 (use periodic table) 1. Uranium-235 has an atomic number of 92 and a mass number of 235. a. How many protons b. How many neutrons c. It emits an alpha particle (p:2, n:2). What atom is left? How many p & n?

  13. Practice 2 (use periodic table) 2. Thorium-231 (90 protons and 141 neutrons) next emits a gamma particle. A gamma is pure energy. What atom remains? Give its name and the number of p and n.

  14. Practice 3 (use periodic table) 3. Thorium-231 also emits an alpha particle. How many protons and neutrons does the daughter have and what is its name?

  15. Practice 4 (use periodic table) 4. Nitrogen-16 is a radioactive element. a. How many protons? b. How many neutrons? c. 16N decays by beta decay, a neutron turning into a proton and emitting an electron. What is the new atom and how many p and n?

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