NUCLEAR CHEMISTRY

Download NUCLEAR   CHEMISTRY

Post on 22-Jan-2016

17 views

Category:

Documents

0 download

Embed Size (px)

DESCRIPTION

NUCLEAR CHEMISTRY. 11 B. 10 B. Isotopes. Same element ( Z ) but different mass number ( A ). Boron-10 has 5 p and 5 n: 10 5 B Boron-11 has 5 p and 6 n: 11 5 B. Isotopes. Except for 1 1 H the mass number is always at least 2 x atomic number. - PowerPoint PPT Presentation

TRANSCRIPT

  • *RadioactivityEmission of particles and/or energy due to a change in the nucleus of an atom.Nuclear Radiation also called Ionizing radiationMeasure with Geiger Counter

    *

    Geiger Counter: Radiation detection

    *

    Types of NUCLEAR Radiation

    *

    Nuclear ReactionsErnest Rutherford found Ra forms Rn gas when emitting an alpha particle.

    1902Rutherford and Soddy proposed radioactivity is the result of the natural change of the isotope of one element into an isotope of a different element.

  • *Nuclear ReactionsorTransmutationsNatural DecaySpontaneous breakdown of unstable nuclei. Called Radioisotopes

    *

    Penetrating Ability

  • *NATURAL Decay:DECAY = Fall apartAlpha DECAYBeta DECAYPositon DECAY

    *

    Nuclear ReactionsAlpha emissionNote that mass number (A) goes down by 4 and atomic number (Z) goes down by 2.Nucleons are rearranged but conserved [mass number (A)] Nucleons = PROTON OR NEUTRON (particle in the nucleus)

    *

    Nuclear ReactionsBeta emissionNote that mass number (A) is unchanged and atomic number (Z) goes up by 1.How does this happen?

    *

    Other Types of Nuclear ReactionsPositron (0+1b): a positive electronK-capture: the capture of an electron from the first or K shell

    An electron and proton combine to form a neutron.0-1e + 11p --> 10n

    *

    Radioactive Decay Series

  • *Writing Nuclear ReactionsParent element = Reactant

    Daughter element = Product

    Radioactivity = radiation produced

  • *Writing Nuclear ReactionsLaw of Conservation of MassL. of C. of ChargeIsotopic Notation Mass # and Nuclear Charge146C = 147N + 0-1e

  • *

  • *

    *

    Stability of Nuclei Heaviest naturally occurring non-radioactive isotope is 209Bi with 83 protons and 126 neutrons There are 83 x 126 = 10,458 possible isotopes. Why so few actually exist?

    *

    Band of Stability and Radioactive DecayIsotopes with low n/p ratio, below band of stability decay, by positron emission or electron capture

    *

    Stability of Nuclei Out of > 300 stable isotopes:EvenOddOddEvenZN15752505

    *

    Binding Energy, EbEb = energy required to separate the nucleus into protons and neutrons. For deuterium, 21H

    21H ---> 11p + 10nEb = 2.15 x 108 kJ/molEb per nucleon = Eb /2 nucleons = 1.08 x 108 kJ/mol nucleons

    *

    Binding Energy/Nucleon

    *

    Calculate Binding EnergyFor deuterium, 21H: 21H ---> 11p + 10nMass of 21H = 2.01410 g/molMass of proton = 1.007825 g/molMass of neutron = 1/008665 g/molm = 0.00239 g/molFrom Einsteins equation: Eb = (m)c2 = 2.15 x 108 kJ/molEb per nucleon = Eb/2 nucleons = 1.08 x 108 kJ/mol nucleons

    *

    Half-LifeSection 15.4 & Screen 15.8HALF-LIFE is the time it takes for 1/2 a sample is disappear.The rate of a nuclear transformation depends only on the reactant concentration.Concept of HALF-LIFE is especially useful for 1st order reactions.

    *

    Half-Life

    Decay of 20.0 mg of 15O. What remains after 3 half-lives? After 5 half-lives?

    *

    Kinetics of Radioactive DecayActivity (A) = Disintegrations/time = (k)(N) where N is the number of atomsDecay is first order, and soln (A/Ao) = -ktThe half-life of radioactive decay ist1/2 = 0.693/k

    *****************************