Known nuclides
PROPERTIES OF FUNDAMENTAL
PARTICLES
• Particle Symbol Charge
Mass
•
(x10 -19 Coulombs) (x10-27kg)
• Proton P
+1.60218
1.672623
• Neutron N
• Electron e
0
-1.60218
1.674929
0.0005486
NUCLEAR STABILITY
Modes 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
+  + E
T1/ 2= 4.48 x 10 9 yrs
•
210Po
206Pb
234Th
++E
T 1/ 2= 138 days
•
256Rf
252No
++E
T1/ 2= 7 msec
•
241Am
237Np
T1/ 2= 433 days
++E
Beta Decay - Electron Emission
P+ +  + Energy
• N
•
90Sr
90Y
+  + Energy
T1/ 2= 30 yrs
14N +  + Energy
• 14C
T1/ 2= 5730 yrs
247Am
247Cm +  + Energy
•
T1/ 2= 22 min
131Xe +  + Energy
• 131I
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
T1/2 = 4.5 x 109yrs
Pb
Figure 21.2:
Decay series
Natural Decay series for Uranium 238
238U
234 Th
234Pa
234U
230 Th
226Ra
222Rn
218Po
218At
214Bi
214Po
=  decay
=  decay
238U
214Pb
210 Tl
210Pb
210Bi
210
Po
206Hg
206Tl
206Pb
-- 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 highenergy particle
accelerator in
Batavia, Illinois.
Source: Fermilab Batavia, IL
Plot of energy versus
the separation distance
Units used for Nuclear Energy Calculations
electron 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
Nucleon
-0.002388 amu x 931.5 Mev / amu
= 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
nucleon
- 0.528461 amu x 931.5 Mev / amu
=
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
mucleon
-1.934205 amu x 931.5 Mev / amu
=
238 nucleons
=
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http://www.pbs.org/wgbh/amex/bomb/sfeature/foxhole.html
http://www.atomicarchive.com/Movies/blastwave3.shtml
Oppenheimer
http://www.atomicarchive.com/Movies/Movie8.shtml
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