1 / 32

CHEMISTRY 1 Nuclear Chemistry

CHEMISTRY 1 Nuclear Chemistry. Chapter 28. NUCLEAR CHEMISTRY. 1896- Antoine Becquerel discovered ___________________ He accidently left uranium ore on top of photographic plates. They became fogged from the exposure. Becquerel had 2 graduate students: _______________ _______________.

kamali
Download Presentation

CHEMISTRY 1 Nuclear Chemistry

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. CHEMISTRY 1Nuclear Chemistry Chapter 28

  2. NUCLEAR CHEMISTRY • 1896- Antoine Becquerel discovered ___________________ • He accidently left uranium ore on top of photographic plates. They became fogged from the exposure. Becquerel had 2 graduate students: _______________ _______________ radioactivity Marie & Pierre Curie

  3. Radioactivity • _______________________- the property by which uranium gives off rays • ______________________-penetrating rays emitted by a radioactive source. • In 1903, the Curies and Becquerel won Nobel prizes for this discovery. Radiation

  4. Types of Radiation • 1. Alpha emission -helium nuclei emitted from a radioactive source • 2 protons & 2 neutrons • 2+charge • Symbol is  • Don’t travel far and are not very penetrating • Stopped by a sheet of paper • Can’t penetrate skin, but dangerous if ingested • Very common with heavy nuclides He Write this

  5. Alpha Decay (α) Lose 2 protons (+2 charge) & 2 neutrons 4 2 He

  6. Examples: Mass # = # protons + # neutrons 238 U  ___ + He Th 92 Atomic # 222 Ra  Rn + He 86 Law of conservation of mass

  7. 226 88 4 2 Ra Rn + He 222 86 Atomic # 88 86 + 2 Mass # 226 222 + 4

  8. electrons • 2. Betaemission - fast moving ___________ formed by the decomposition of a neutron of an atom. The neutron breaks into a proton and an electron. The proton stays in the nucleus and the electron is ejected. (net effect: neutron changes into proton) • Write this: n  H + e

  9. Much smaller than alpha particles • Symbol is  • Charge is -1 • Much more penetrating than alpha particles • Stopped by aluminum foil or thin pieces of wood e Write this C N + e

  10. 0 -1 β Beta Decay (β) Lose electron (-1 charge, no mass) 14 6 C N + β 14 7 0 -1

  11. electromagnetic radiation • 3. Gamma emission - _________________ _____________ (high energy) emitted from a nucleus as it changes from an excited state to a ground energy state. • Often emitted along with  or  radiation • Symbol is  • Has no mass & no charge • High energy photon U He + Th + 2 

  12. the emission of gamma rays is one way that a nucleus with excess energy (in an excited nuclear state) can relax to its ground state • Extremely penetrating, very dangerous • Stopped somewhat by several feet of concrete or several inches of lead

  13. Gamma Emission (γ) No mass, no charge, loses just energy γ 0 0

  14. 4. Positron emission- ___________________________________ • e • Antimatter • Net effect: changes proton to a neutron • Occurs when neutron/proton ratio is too small Particle with the mass of an electron but a positive charge Write this (the 0 and the +1) Na  e + Ne

  15. Alpha radiation cannot penetrate the skin and can be blocked out by a sheet of paper, but is dangerous in the lung. Beta radiation can penetrate into the body but can be blocked out by a sheet of aluminum foil. Gamma radiation can go right through the body and requires several centimeters of lead or concrete, or a meter or so of water, to block it.

  16. Nuclear Transformation (Transmutation)- ____________________________________ • bombarding with alpha particles • Bombarding with neutrons Changing one element into another N + He  O + H Write these U + n  U

  17. Fill in the blanks (not in your notes): 0 1 60 26 e • Co Ni + ____ • Am Np + ____ • Th He + ____ • N + ____ C + H 60 27 4 2 He 241 95 237 93 226 88 Ra 230 90 4 2 1 0 n 14 7 14 6 1 1

  18. Half-life (t1/2) • the time required for ½ of the atoms of a radioisotope to emit radiation and decay to products • the longer the half-life, the more _____________ the isotope • varies from fractions of a second to millions of years stable

  19. Examples • Nitrogen-13 decays to carbon-13 with a half-life of 10 minutes. How long is 4 half lives? 4 half lives X 10 min/half life = 40 min.

  20. If you start with 2.00 g of nitrogen-13 how many grams will remain after 4 half lives? 1 2 3 2.00 g 1.00 g 0.500 g 0.250 g 4 0.125 g

  21. Phosphorous-32 has a half-life of 14.3 yr. How many grams remain after 57.2 yr from a 4.0 g sample? 57.2 yr = 4 half-lives 14.3yr / half-life 1 2 3 4 4.0 g 2.0 g 1.0 g 0.50 g 0.25 g

  22. Carbon-14 dating • Carbon-14 is continuously produced in the ____________ when high energy neutrons from outer space collide with nitrogen-14 in the air. atmosphere N + n  C + H

  23. Carbon-14 combines with oxygen to form CO2 which is incorporated into plant materials. As long as the plant or animal is alive, decaying carbon-14 is continuously replaced. After death, the carbon-14 decays at a steady rate. Carbon-14 decays to Nitrogen-14 C  e + N

  24. The proportion of carbon-14 in the atmosphere is relatively constant. The carbon-14/carbon-12 ratio is used to identify the age of wood, cloth and other ______________ artifacts. The half-life of carbon-14 is _______________ years. • Only works for organic materials • Adjusted for change in % C-14 over the years organic 5730

  25. Example • If the C-14 in a fossil sample is only 1/4 what it is in living organisms, how old is the object? To have ¼ remaining, 2 half lives have passed. 2 X 5730 yr = 11,460 yr.

  26. Fission - splitting a heavy nucleus into two nuclei with smaller mass numbers. • used for _____________________ • production of ______________causes a chain reaction (which must be controlled) • 1 kg of uranium-235 is equivalent to 20,000 tons of dynamite nuclear energy n + U  Ba + Kr + 3 n neutrons

  27. FISSION: splitting of atoms Fission – splitting of atoms.

  28. heat steam • Fission in a nuclear reactor is carefully controlled. Much of the energy is _______. This energy is used to produce _________ and subsequently, __________________. • A _________________(usually water) is needed. • The water (or carbon) also acts as a moderator. It _____________the neutrons down so that they can be captured by the U-235 fuel. • Control rods made of _______________ are present to absorb excess neutrons to slow down the reaction. They can be raised or lowered into the reactor core. electricity coolant slows cadmium

  29. Fusion- combining two light nuclei to form a heavier, more stable nucleus • stars produce their energy this way • Currently __________________ are necessary in order to initiate fusion • possible future energy source high temperatures 4 H + 2e  He + energy

  30. FUSION: two nuclei combine to form a heavier nuclei Fusion – two nuclei combine to form a heavier nucleus.

  31. Proton-proton chain reaction Proton-proton chain reaction Fusion reaction in our Sun’s core.

More Related