CHAPTER 10 NUCLEAR CHEMISTRY

Section 10.1 I. Radioactivity

I. Radioactivity Process in which an unstable atomic nucleus emits charged particles of energy. A. Nuclear Decay – Radioisotope - any atom containing an unstable nucleus *During radioactive decay, atoms of that element can change into atoms of a different element together

B. Types of Nuclear Decay Scientist can detect a radioactive substance by measuring the nuclear radiation it gives off Nuclear radiation – charged particles and energy emitted from the nuclei of radioisotopes (there are 3 types: alpha, beta, and gamma)

1. Alpha Particles Alpha particles – a positively charged particle, emitted by some radioactive nuclei that consists of 2 protons and 2 neutrons Ernest Rutherford- noted for discovering the nucleus, named them “alpha” rays (later he discovered they were particles (2 protons and 2 neutrons) They didn’t travel trough materials They remove electrons (ionize) from matter

Alpha Decay (42He) 22688 Ra 22286 Rn + 42He 226– 4 = 222 88-2= 86 change in proton number

2. Beta Decay Beta Particles- an electron emitted during the radioactive decay of a neutron in an unstable nucleus Fast moving electrons- travel easily through paper ( stop by 3mm aluminum or 10mm of wood) They ionize atoms – lose energy

Beta Decay( 0-1e) 146C 147 N + 0-1e 14+0=14 6+1= 7

3. Gamma Decay Gamma rays are waves, not particles. This means that they have no mass and no charge, but can still do damage. Gamma rays have a high penetrating power – go through 7 cm of lead

Alpha-Beta-Gamma

C. Effects of Nuclear Radiation You are exposed to nuclear radiation everyday Background radiation – nuclear radiation that occurs naturally in the environment Water, rocks, plants, and animals all contribute to background radiation

2.Dangers of Nuclear Radiation * Nuclear radiation can ionize atoms in living tissue The outer skin keeps most radiation out of the body Nuclear radiation( gamma ray ) can cause burns in the skin and destroys bone marrow cells which red and white blood cells

3.High concentrations of radon gas Radon 222 is produced in the Earth’s crust. Outside the level is low BUT overtime a build up in basements produces alpha particles that can be inhaled and cause damage to lung tissue.

4. Radiation exposure over time Common Symptoms Decrease in white blood cells Hair loss Sterility Destruction and death of bones Cancer Genetic mutations: birth defects

Nuclear Power ADVANTAGES- Nuclear Fission doesn’t produce gaseous pollutants (generates energy) Generate Electricity DISADVANTAGES Possible escape of radioactive isotopes in the environment Power plants can only operate for 40 years

Power plants Power plants can only operate for 40 years They are expensive to build Nuclear waste has to be stored safely These plants have to be built where they are free from earth quakes, little water and barley populated

Detecting Nuclear Radiation Devices that are used to detect nuclear radiation include Geiger counters and film badges . Geiger counters – uses a gas filled tube to measure ionizing radiation Film badges – indicates the the amount of radiation exposure for the person wearing the badge

Section 10.2 Rates of Nuclear Decay

A. Half- Life Half- Life – time required for half a sample of radioactive decay How do you find out how old a rock is?

Half- life is a measure of how quickly a substance decays

B. Radioactive Dating Carbon reacts with the Oxygen in the atmosphere and forms carbon dioxide Plants use carbon dioxide during photosynthesis and keep the ratio of carbon-14 to carbon-12 in the atmosphere constant When something dies, its carbon-14 begins to decay If the ratio of C14 to C12 in a fossil is ½ of the atmospheric ratio, then the fossil is 1 half-life or about 5730 years old.

ARTIFICIAL TRANSMUTATION SECTION 10.3 ARTIFICIAL TRANSMUTATION

A. Nuclear Reactions in the Laboratory Scientist can perform artificial transmutation by bombarding atomic nuclei with high energy particles such as protons, neutrons, or alpha particles.

B. Transuranium Elements Elements with the atomic numbers greater than 92 All are radioactive Generally not found in nature 1977, NASA, powered the Voyager 1 and 2 with alpha decay of plutonium

C. Particle accelerators Charged particles can be accelerated to speeds very close to the speed of light. The fast moving particles are guided toward a target, where they collide with atomic nuclei Scientist have developed over 300 isotopes with this device

Section 10.4 FISSION AND FUSION

A. NUCLEAR FORCES Strong nuclear force is the attractive force that binds protons and neutrons together in the nucleus Over very short distances, the strong nuclear force is much greater than the electron forces among protons

B. Fission Splitting of atomic nucleus into two smaller pieces Nuclear fission – tremendous amounts of energy can be produced from very small amounts of mass Converting energy into mass E=mc2 E=energy m= mass c2 = speed of light ( 3.0 x 108m/s) Lise Meitner- correctly predicted that fission releases large amounts of energy

Triggering a chain reaction Chain reaction – neutrons released during the splitting of an initial nucleus trigger a series of nuclear fissions Critical Mass - the smallest possible mass of fissionable material that can sustain a chain reaction

Nuclear Energy From Fission Today nuclear power plants generate 20% of electricity in the United States. The don’t emit air pollutants Workers have to wear protective clothing

Nuclear Chemistry History 1896 – Antoine Becquerel discovers radioactivity in Uranium 1898- Marie and Pierre Curie discover radioactive elements (polonium and radium) 1905- Albert Einstein - E=mc2 provides the basis for nuclear power 1932 – First atom smasher(particle Accelerator) is used by John Cockcroft and Ernest Walton 1938 - Otto Hahns & Strassman produced nuclear fission

Nuclear Chemistry History 1942 – The first controlled self-sustaining nuclear chain is achieved by Enrico Fermi’s research group in Chicago 1945 – United States explodes first atom bomb in test near Alamagordo, New Mexico 1951 – Electricity from nuclear fission produced at National Reactor Testing Station, Idaho 1960 – Willard Libby wins the Nobel Prize for developing carbon – 14 dating 1986 – Partial meltdown Chernobyl power plant

C. Fusion Fusion is the process in which the nuclei of two atoms combine Fusion requires extremely high temperatures Fusion may someday provide an efficient and clean source of electricity Scientist face two problems in designing a fusion reactor: they need to archive the high temperature required to start the reaction and they must contain plasma