Nuclear Chemistry

Nuclear ChemistryNuclear Chemistrystudy of changes in structure of nuclei and subsequent changes in chemistry2Stability of an AtomAll elements after Bismuth (atomic #83) are unstableUnstable atoms have the wrong ratio of protons and neutronsUnstable atoms become stable by changing their nucleus: this is called DECAY3Writing Nuclear Equations

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Types of Nuclear ReactionsRadioactive Decay Nuclear Bombardment Radioactive Decaynucleus decays spontaneously giving off an energetic particleDiscovered by Antoine Henri Becquerel in 1896He saw that photographic plates developed bright spots when exposed to uranium metals

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Isotopic Symbolism The penetrating power of radiation.

9Types of radioactive decayalpha particle emission beta emission positron emissionelectron capturegamma emissionAlpha decayalpha particle emissionloss of a helium nucleus.

Example:Types of radioactive decayalpha particle emission beta emission positron emissionelectron capturegamma emissionBeta decaybeta emission A neutron splits into a proton and electron which is spit out as a particle.

Example:

Types of radioactive decayalpha particle emission beta emission positron emissionelectron capturegamma emissionPositron Emissionpositron emission A proton kicks out positive charge (a positron, b+) to become a neutron.

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Types of radioactive decayalpha particle emission beta emission positron emissionelectron capturegamma emissionElectron Captureelectron capture (EC)an electron (from inner shell) is sucked into the nucleus to combine with a proton produces a neutron.

Example:

Types of radioactive decayalpha particle emission beta emission positron emissionelectron capturegamma emissionGamma Emissiongamma emission emission of energy (photon) from an unstable nucleus.

Types of Nuclear ReactionsRadioactive Decay Nuclear Bombardment Types of Nuclear ReactionsRadioactive Decay Nuclear Bombardment Nuclear Bombardment Reactionsshoot a high energy particle at the nucleus of another atom

Transmutation changing one element to another by shooting a nuclear particle at its nucleus.

Fusion reactions in which two or more elements "fuse" together to form one larger element, releasing energy in the processAs does the sun: 21H + 31H 42He + 10n10 x more energy/gram than fission

A flare ejected from the surface of the sun.

Courtesy NASA24A flare ejected from the surface of the sun. The suns energy comes from a fusion reaction that converts hydrogen to helium.X-ray examination of luggage at a security station.

25An image of a thyroid gland obtained through the use of radioactive iodine.

26Images of human lungs obtained from a -ray scan.

27Images of human lungs obtained from a -ray scan. A compound containing radioactive technetium-99m was the source of the radiation.A cancer patient receiving radiation therapy.

28Fissionreactions in which an atom's nucleus splits into smaller parts, releasing a large amount of energy in the processMeitner, Strassmann, and Hahn discovered fission: splitting of uranium-235Instead of making heavier elements, created a Ba and Kr isotope plus 3 neutrons and a lot of energyTo make a bomb, however, need critical mass = enough mass of U-235 to produce a self-sustaining rxn

Nuclear Reactions as an Energy Source

Uranium-235, a source of nuclear power.A typical fission reaction of U-235.

31Schematic diagram of the cascading effect of a typical chain reaction initiated by a single neutron.

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The worlds first atomic explosion, July 16, 1945 at Alamogordo, New Mexico.

The uranium bomb, 3m (10 ft) long and 0.7 m (2.3 ft) in diameter, was called Little Boy.

35The operation of fission bombs.

36Remains of a building after the explosion of the uranium bomb at Hiroshima, August 6, 1945.

37Schematic diagram of a nuclear power plant.

38The nuclear power plant at Chernobyl, after the accident of April 16, 1986.

39Nuclear powerIn America, about 20% electricity generated by nuclear fissionImagine: Nuclear-powered carFuel = pencil-sized U-cylinderEnergy = 1000 20-gallon tanks of gasolineRefuel every 1000 weeks (about 20 years)End41