nuclear chemistry

Download NUCLEAR CHEMISTRY

If you can't read please download the document

Post on 04-Jan-2016

9 views

Category:

Documents

0 download

Embed Size (px)

DESCRIPTION

NUCLEAR CHEMISTRY. FYI: Historical Perspective. Henri Becquerel 1896 - Discovers natural radioactivity. FYI: Historical Perspective. Marie Sklodowska, Polish chemist marries Pierre Curie, French physicist Marie died from leukemia caused by her exposure to radiation - PowerPoint PPT Presentation

TRANSCRIPT

  • NUCLEAR CHEMISTRY

  • FYI: Historical PerspectiveHenri Becquerel1896 - Discovers natural radioactivity

  • FYI: Historical PerspectiveMarie Sklodowska, Polish chemist marries Pierre Curie, French physicistMarie died from leukemia caused by her exposure to radiationPierre was killed while crossing the street when he was hit by a vegetable wagon.

  • FYI: Historical PerspectiveEarnest Rutherford1899 Discovers alpha, beta and gamma radiation

  • Nuclear ReactionsInvolve changes in the composition of nucleiAccompanied by the release of tremendous amounts of energy

  • Nuclear FissionThe splitting of a heavy nucleus into lighter nuclei

  • Nuclear FusionThe combination of light nuclei to produce a heavier nucleus

  • NuclidesDifferent atomic forms of all elementsMost small nuclides have equal # of protons and neutronsSome nuclides have magic #s of protons and neutrons and are especially stable

  • The neutron-to-proton ratio determines the stability of the nucleusFor low atomic #s:Equal #s of protons and neutrons

    Above atomic #20:More neutrons than protons

  • Nuclei whose neutron-to-proton ratio is unstable undergo radioactive decay by emitting 1 or more particles and/or electromagnetic rays:

  • Nuclei whose neutron-to-proton ratio is unstable undergo radioactive decay by emitting 1 or more particles and/or electromagnetic rays:helium nucleuselectronhigh energy radiationproton, H nucleusneutron4.00262+0.000551-001.00731+1.00870lowlow-medhighlow-medvery high

  • Comparing penetrating ability

  • Alpha Particle DecayExample 1: Radium-226 transmutates by alpha decay. Write the nuclear equation that represents this process.or

  • Beta Particle DecayExample 2: Write the nuclear equation for the beta-decay of boron-12.++or

  • Gamma RadiationExample 3: Write the nuclear equation representing gamma radiation given off by the unstable radionuclide cobalt-60.

  • Nuclear Fission & Fusion

  • FISSION: a heavy nucleus splits into 2 lighter nucleisome elements undergo fission spontaneouslysome elements can be induced to undergo fission when bombarded with other particles (e.g. neutrons)

  • FUSION: 2 nuclei combine to form a heavier nucleusthe sun is a tremendous fusion reaction; the major fusion reaction in the sun is thought to be:

    both fission & fusion release large amounts of energy (fusion more than fission)

  • The Atomic Bomb (FISSION)when the nucleus of U-235 splits, 2 isotopes are formed, plus neutrons are emittedthese neutrons collide with other U-235 atoms, causing them to undergo fission; they release neutrons, and so onThe result - CHAIN REACTION!!

  • FISSION

  • CHAIN REACTION!!!

  • The Atomic Bomb (FISSION)

  • The Atomic Bomb (FISSION)

  • CRITICAL MASSThe minimum mass of fissionable material that must be used to sustain a chain reaction

  • One type of bombLittle Boy: U-235 (Hiroshima)

    Fat Man: Pu-239 (Nagasaki)subcritical mass of U-235subcritical mass of U-235TNT (dynamite)

  • Nuclear Reactors (controlled FISSION)

  • Nuclear Reactors (FISSION)use subcritical masses of fissionable materialCORE: contains fuel pins made of U-235; interspersed among the pins are control rodscontrol rods: absorb neutronspull rods out of core: fission increasespush rods back into the core: fission decreasesSafety feature: if power is lost, rods will automatically fall into the core and shut the reaction down.

  • Nuclear Reactors (FISSION)The energy produced by breaking down the atom is a very poor kind of thing. Anyone who expects a source of power from the transformation of these atoms is talking moonshine.Ernest Rutherford

  • Nuclear Reactors (FISSION)

  • Nuclear Power Plants

  • Nuclear Power Plants

  • Nuclear Power Plants

  • TO GENERATE ELECTRICITY:Fission heats up water in vessel and heat is carried away.This heat is used to heat up water in a second system, which turns into steam.Steam turns turbine of a generator.Generator makes electricity.

  • PROS OF NUCLEAR ENERGY:no air pollutionenormous amt. of energy releasedalternative to using our rapidly decreasing fossil fuels

  • CONS OF NUCLEAR ENERGYcontainers for waste products may erode or breakthermal pollution (heated water returned to rivers, etc.)potential theft of fuel (Pu-239) for use in weapons

  • Controlled Nuclear FUSIONPROS:A very abundant supply of energy world wide.Environmentally cleanNo creation of weapon materialsNo chance of runaway reactions leading to accidentsCONS:It doesnt work; at least not yet

  • Nuclear Fusion"Every time you look up at the sky, every one of those points of light is a reminder that fusion power is extractable from hydrogen and other light elements, and it is an everyday reality throughout the Milky Way Galaxy." Carl Sagan, Spitzer Lecture, October 1991

  • Nuclear FusionObstaclesHOT plasma at least 100 million CHigh density plasmaContainment of plasmaConfinement time

  • Rates of Decay & Half LifeRadionuclides have different stabilities and decay at different rates.

  • Integrated Rate Equation

    whereA = the amt. of decaying sample remaining at some time, tAo= the amt. of sample present at the beginning k = rate constant; different for each radionuclidet = time

  • Integrated Rate EquationOR

    whereN = # of disintegrations per unit of time; relative activityNo= original activity

  • HALF-LIFE= the amount of time required for half of the original sample to decay

    Chart1

    100

    50

    25

    12

    6

    3

    2

    1

    Time

    Amount

    Half Life

    Sheet1

    2100

    450

    625

    812

    106

    123

    142

    161

    Sheet1

    Time

    Amount

    Half Life

    Sheet2

    Sheet3

  • HALF-LIFE= the amount of time required for half of the original sample to decayParentDaughter

    Chart2

    2000

    100100

    50150

    25175

    12188

    6194

    3197

    2198

    1199

    Amount

    Time

    Sheet1

    02000

    2100100

    450150

    625175

    812188

    106194

    123197

    142198

    161199

    Sheet1

    00

    00

    00

    00

    00

    00

    00

    00

    00

    Amount

    Time

    Sheet2

    Sheet3

  • HALF-LIFEHalf-life = the amount of time required for half of the original sample to decay

  • Example: Cobalt-60 decays with the emission of beta particles and gamma rays, with a half-life of 5.27 years. How much of a 3.42 g of cobalt-60 remains after 30.0 years?How do you solve for A???

  • Take the ANTILOG (10x) of both sides.

  • Example: Cobalt-60 decays with the emission of beta particles and gamma rays, with a half-life of 5.27 years. How much of a 3.42 g of cobalt-60 remains after 30.0 years?

  • Uses of RadionuclidesRadiocarbon dating: the ages of specimens of organic origin can be estimated by measuring the amount of cabon-14 in a sample.

  • Example: A piece of wood taken from a cave dwelling in New Mexico is found to have a carbon-14 activity (per gram of carbon) only 0.636 times that of wood today. Estimate the age of the wood. (The half-life of carbon-14 is 5730 years.)

  • Example: A piece of wood taken from a cave dwelling in New Mexico is found to have a carbon-14 activity (per gram of carbon) only 0.636 times that of wood today. Estimate the age of the wood. (The half-life of carbon-14 is 5730 years.)t=3744 yrs = 3740 yrs

  • Uses of Radionuclides***NOTE: Objects older than 50,000 years have too little activity to be dated accurately using carbon dating; instead the following methods are used:

    Potassium-40 decays to argon-40: half-life = 1.3 x 109 yearsUranium-238 decays to lead-206: half-life = 4.51 x 109 years

  • Example: A sample of uranium ore is found to contain 4.64 mg of uranium-238 and 1.22 mg of lead-206. Estimate the age of the ore.

  • Example: A sample of uranium ore is found to contain 4.64 mg of uranium-238 and 1.22 mg of lead-206. Estimate the age of the ore.