known nuclides properties of fundamental particles particle symbol charge mass (x10 -19 coulombs)...
TRANSCRIPT
Known nuclides
PROPERTIES OF FUNDAMENTAL PARTICLES
• Particle Symbol Charge Mass • (x10 -19 Coulombs) (x10-27kg)• Proton P +1.60218 1.672623
• Neutron N 0 1.674929
• Electron e -1.60218 0.0005486
NUCLEAR STABILITYModes of Radioactive Decay
• Alpha Decay - Heavy Isotopes - 42He+2-
• Beta Decay - Neutron Rich Isotopes - e - -
• Positron Emission -Proton Rich Isotopes - • Electron Capture - Proton Rich Isotopes• x - rays• Gamma-ray emission( - Decay of nuclear • excited states• Spontaneous Fission - Very Heavy Isotopes
Alpha Decay -Heavy Elements• 238U 234Th + + E
T1/ 2= 4.48 x 10 9 yrs
• 210Po 206Pb + + E T 1/ 2= 138 days
• 256Rf 252No + + E T1/ 2= 7 msec
• 241Am 237Np + + E T1/ 2= 433 days
Beta Decay - Electron Emission
• N P+ + + Energy
• 90Sr 90Y + + Energy T1/ 2= 30 yrs• 14C 14N + + Energy
T1/ 2= 5730 yrs• 247Am 247Cm + + Energy
T1/ 2= 22 min• 131I 131Xe + + Energy T1/ 2 = 8 days
Natural Decay Series of Existing Isotopes
40K 40Ar T1/2 = 1.29 x 109yrs
232 Th 208 Pb T1/2 = 1.4 x 1010yrs
235U 207 Pb T1/2 = 7 x 108yrs
238U 206 Pb T1/2 = 4.5 x 109yrs
Figure 21.2: Decay series
Natural Decay series for Uranium 238
238U 234 Th 234Pa
234U 230 Th 226Ra 222Rn 218Po 214Pb 218At 214Bi 210 Tl
214Po 210Pb 206Hg
= decay 210Bi 206Tl
= decay 210 Po 206Pb
238U -- 8 decays and 6 decays leaves you with -- 206Pb
The decay of a 10.0 -g sample of strontium-90 over time.
Accelerator tunnel at Fermilab, a high-energy particle accelerator in Batavia, Illinois.
Source: Fermilab Batavia, IL
Plot of energy versus the separation distance
Units used for Nuclear Energy Calculationselectron volt - (ev) The energy an electron acquires when it moves through a potential difference of one volt:
1 ev = 1.6 x 10-19J
Binding energies are commonly expressed in units of megaelectron volts (Mev)
1 Mev = 106 ev = 1.6 x 10 -13J
A particularly useful factor converts a given mass defect in atomic mass units to its energy equivalent in electron volts: 1 amu = 931 x 106 ev = 931 Mev
Binding energy per nucleon as a function of mass number.
Binding Energy per Nucleon of Deuterium
Deuterium has a mass of 2.01410178 amu.
Hydrogen atom = 1 x 1.007825 amu = 1.007825 amu Neutrons = 1 x 1.008665 amu = 1.008665 amu 2.016490 amu
Mass difference = Theoretical mass - actual mass = 2.016490 amu - 2.01410178 amu = 0.002388 amu
Calculating the binding energy per nucleon:
Binding Energy -0.002388 amu x 931.5 Mev / amu Nucleon 2 nucleons
=
=
Calculation of the Binding Energy per Nucleon for Iron- 56
The mass of Iron -56 is 55.934939 amu, it contains 26 protons and 30 Neutrons
Theoretical Mass of Fe - 56 : Hydrogen atom mass = 26 x 1.007825 amu = 26.203450 amu Neutron mass = 30 x 1.008665 amu = 30.259950 amu 56.463400 amu
Mass defect =Actual mass - Theoretical mass: 55.934939 amu - 56.46340 amu = - 0.528461 amu
Calculating the binding energy per nucleon:
Binding Energy - 0.528461 amu x 931.5 Mev / amu nucleon 56 nucleons=
=
Calculation of the Binding Energy per Nucleon for Uranium - 238
The actual mass of Uranium - 238 = 238.050785 amu, and it has 92 protons and 146 neutrons
Theoretical mass of Uranium 238: Hydrogen atom mass = 92 x 1.007825 amu = 92.719900 amu neutron mass = 146 x 1.008665 amu = 147.265090 amu 239.984990 amu
Mass defect = Actual mass - Theoretical mass: 238.050785 amu - 239.984990 amu = - 1.934205 amu
Calculating the Binding Energy per nucleon:
Binding Energy -1.934205 amu x 931.5 Mev / amu mucleon 238 nucleons=
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Both fission and fusion produce more stable nuclides and are thus exothermic.
Upon capturing a neutron, the 235U nucleus undergoes fission to produce two lighter nuclides, free neutrons (typically three), and a large amount of energy.
Representation of a fission process in which each event produces two neutrons, which can go on to split other nuclei, leading to a self-sustaining chain reaction.
If the mass of the fissionable material is too small, most of the neutrons escape before causing another fission event; thus the process dies out.
Nuclear power plant
Breeder reactor at a nuclear power plant in St. Laurent-Des Eaux, France.
Source: Stock Boston
A Uranium "button" for use as a fuel in a nuclear reactor.
Schematic of a reactor core