nuclear chemistry


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NUCLEAR CHEMISTRY. nuclear chemistry/physics : processes that occur in the NUCLEUS—these are not chemical reactions!. Objectives. What is radiation? Understand the meaning of terminology related to radioactivity. Know the three main types of nuclear radiation. - PowerPoint PPT Presentation


Nuclear Chemistry


nuclear chemistry/physics:processes that occur in the NUCLEUSthese arenot chemical reactions!ObjectivesWhat is radiation? Understand the meaning of terminology related to radioactivity.Know the three main types of nuclear radiation.Be able to write correct nuclear equations.Understand the concept of penetration power.Radioactivity1896: Henri Becquerel discovers that uranium affects photographic film.Marie Curie calls it radioactivity: the process of materials emitting raysradiation: the rays/particles given off by a radioactive sourceradioisotope: unstable isotope that emits radiation

Three Types of Radiationa: Alpha (helium nucleus emitted)

Total charge (subscript) and mass (superscript) must be conserved.b: Beta (electrons emitted as no p+ + e-)

g: Gamma (high energy EM radiation)

Radiation Problems

Penetration Power

ObjectivesWhy do atoms decay? Understand the concept of nuclear stability and be able to determine the type of radioactive decay for various isotopes.Be able to determine the products of various transmutation reactions.Nuclear TransformationsProtons repel, but the nuclear strong force can hold p+ and no together.Neutrons are needed to supply this force, but a stable p+ to no ratio is necessary.Elements decay to create a stable ratio.

Transmutationstransmutation: an atom is converted into a different atom (of a different element)radioactive decay

*positron: positive electron (antimatter)*neutrino (v): may be massless

(nucleus is too heavy)(too many neutrons)(too many protons)Decay Series

Transmutationsbombardment: particles collide with the nucleus to cause transmutations (like bowling!)

The discovery of the p+ and the no were achieved using bombardment.

RutherfordObjectivesHow long does it take for a nucleus to decay? Understand the concept of half-life.Simulate the radioactive decay of an imaginary radioisotope and determine the half-life of the isotope.Be able to make simple half-life calculations.

Half-Lifehalf-life (T1/2): the time it takes for one-half of the nuclei of a radioisotope to decay to products

64 nuclei 32 16 8 4 2 1

If T1/2 = 200 years, it takes six half-lives (1200 years) to decay from 64 to 1.

Measuring Nuclear DecayFermium has a half-life of 100.5 days. How much of a 5.2 mg sample of fermium will remain after 365 days?

ObjectivesWhat is nuclear energy? Understand the processes of nuclear fission.Be able to discuss how various technologies employ nuclear fission.Nuclear Fissionfission: the splitting of a large nucleus into smaller fragmentsthe products have less mass than the reactantsmass is converted into energy (E=mc2)

Nuclear Fission Power Nuclear power plants use controlled nuclear fission to release energy slowly.Heat creates steam that generates electricity.

Fission Reactor Core

Three-Mile Island

The Fission A-BombThe WWII bombs used uncontrolled nuclear fission. Material must have a critical mass to explode.Test bomb/Nagasaki: implosion of Pu-239 Hiroshima: gun-type with U-235

Nuclear Fusionnuclear fusion: small nuclei combine and release more energy than fission reactions.

The energy (E=mc2) is mostly in the form gamma rays, positrons, and neutrinos.

Thermonuclear WeaponsModern nukes use fission to start a fusion reaction.These weapons are about 100 times more powerful than the A-bomb (1.2 megatons vs. 15 kilotons of TNT).