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Chapter 21 Nuclear chemistry
Particles • α alpha particle 4He a helium nuclei • β beta particle…an electron 0e • -1 • γ gamma particle, no mass, no charge 2p + 2n & NO electrons!
Proton 1H or 1p • Neutron 1n • Positron 00e • +1
Alpha emission • Beta emission • Gamma emission
Positron emission • Electron capture • OR (K-capture) Decay = decomposition
p 2e-) 8e-) 8e-) 2e-) • K L M N O P …… p+ n
New Zealand currency – • Ed Hillary, • Kate Sheppard, • QEII, • ApiranaNgata, • Ernest Rutherford -
Nuclear equations Decay = decomposition
p. 899 Belt of stability
Subatomic Particles • Particle • Charge • Mass (g) • Nomenclature • alpha • 2+ • 6.64e-24 • 42He 42α • beta • 1- • 6.64e-24 • 0-1e 0-1β • gamma • 0 • 0 • 00γ • proton • 1+ • 6.64e-24 • 11H 11p • neutron • 0 • 6.64e-24 • 0n • elelctron • 1- • 9.11e-28 • 0-1e • positron • 1+ • 9.11e-28 • 0+1e
Other Considerations • Other Factors to Nuclear Stability• Magic numberProtons with - 2, 8, 20, 28, 50 or 82Neutrons with - 2, 8, 20, 28, 50, 82 or 126• Nuclei with even # of protons and neutrons more stable than with any odd number of protons and neutrons.
• Magic number correspond to filled, closed-shell nucleon configuration.• Pairs of protons and neutrons analogous to pair of electrons in the atom.
First order decay • t 1/2 = .693/k • ln([A]o/[A]t) = kt
Shroud • Of • Turin
Nuclear Binding Force • Mass defect - Difference between mass the nucleus and the masses of nucleon.Binding Energy - The energy required to separate a nucleus into its nucleons.E=mc2 → E(binding energy) = m(mass defect) c2
Mass of nuclei < ∑mass nucleons Mass of helium nucleus = 4.00150 amuMass of ∑nucleons = 4.03190 amuMass defect = 0.03040 amu (Binding Energy)
Average binding Energy per nucleon increases to a maximum at a mass of 50 to 60 and decreases slowly thereafter. Fusion (bring nuclei together) is exothermic for low mass number and fission (splitting of nuclei) is exothermic for high mass number.
Nuclear Fission • Splitting of heavy nuclei is exothermic for large mass numberIn a nuclear Fission Process:• Neutrons move slowly because it is absorb by the nucleus.• 235U nucleus split into different daughter nuclei and 3.5•1011 J / nucleus• Every 235U nucleus produced 2.4 neutrons.
Each neutron produced can cause fission to another 235U• Number of fission and energy increase rapidly.• Eventually a chain reaction forms and without control an explosion.
Nuclear Equation: The process • Radionuclides - spontaneously emit particles and radiation which can be expressed by a nuclear equationSpontaneous Emission: Mass and charge are conserved.
Three quarks for Muster Mark! • Sure he has not got much of a bark • And sure any he has it's all beside the mark. • —James Joyce, FinnegansWake.