Lecture 28 (4/1/13)
• Radioactive Decay:
o 1 Order:
N t n
Where n = the number of halflives.
Particle with mass of an electron but with a positive charge.
Particles that are charge opposites of normal subatomic particles
(e.g., electron / positron).
o Collision of matter/antimatter particles results in annihilation; all mass
converted to energy in the form of γrays (i.e. positron and electron come
together and then seize to exist > produce high energy gamma rays,
matter > energy)
Lecture 29 (4/3/13)
• Fusion Reactors: 8
o Hightemperature reactions between deuterium and tritium (T = 1.5 × 10
o Neutrons produced initiate other reactions
o Hightemperature reactions produce an incandescent plasma which is
contained by strong magnetic fields.
• Nuclear Binding Energies:
o Binding Energy (BE):
The energy released when nucleons combine to form a nucleus.
Depends on “mass defect.”
o Mass Defect (Δm):
Difference between the mass (in kg) of a stable nucleus and the
individual nucleons that comprise it.
o E = (Δm)c (Remember: 1 joule = 1 kg∙(m/s) )
• Stability of Nuclei:
o Belt of stability:
Region on a graph
of the number of neutrons vs number of protons that includes all
• Predicting Modes of Decay:
o Nuclides above the belt of stability:
Neutron rich; undergo βdecay (loses beta particle).
14 14 0
6C → 7N + -1 o Nuclides below the belt of stability:
Neutron poor; undergo positrondecay (positron emission > out
comes positive charge) or electron capture.
11C → 11B + β 0
6 5 1
11 0 11
6C + -1e → 5 B
• Nuclear Fission:
o Nuclear Fission:
Nuclear reaction in which a heavy nucleus splits into two lighter
nuclei; usually accompanied by release of one or more neutrons.
o Chain Reaction:
A selfsustaining series of fission reactions in which neutrons