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Nuclear Physics. Nuclear Structure. Nucleus – consists of nucleons (neutrons and protons) Atomic Number Z  number of protons Atomic Mass Number A  nucleon number  total number of neutrons and protons. Atomic Radius. r = (1.2 x 10 -15 m) A 1/3 r  radius

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nuclear structure
Nuclear Structure
  • Nucleus – consists of nucleons (neutrons and protons)
  • Atomic Number Z  number of protons
  • Atomic Mass Number A  nucleon number

 total number of neutrons and protons

atomic radius
Atomic Radius
  • r = (1.2 x 10 -15 m) A 1/3

r  radius

A  atomic mass number

strong nuclear force
Strong Nuclear Force
  • One of three fundamental forces that have been discovered (others  gravitational force, electroweak force)
  • Almost independent of electric charge
  • Nearly the same nuclear force of attraction exists between 2 protons, 2 neutrons, or between a proton and a neutron.
strong nuclear force1
Strong Nuclear Force
  • Range  short; very strong when nucleons are as close as 10-15 m

 zero at larger distances

  • This limited range prevents extra neutrons from balancing longer range electric repulsions of extra protons and atoms become unstable
  • Bismuth  largest stable nucleus
radioactivity
Radioactivity
  • All nuclei above bismuth , Z > 83, will have unstable nuclei and spontaneously break apart or rearrange structure of internal structure
  • This spontaneous disintegration or rearrangement is radioactivity
nuclear binding energy
Nuclear Binding Energy
  • The required energy to break a nucleus apart
  • DE = (Dm)c2

DE  binding energy

Dm  mass defect of the nucleus

(the difference in mass of the nucleus and the individual masses of the separated protons and neutrons)

c  speed of light

radioactive decay
Radioactive Decay
  • When unstable or radioactive nuclei disintegrate spontaneously particles or high-energy photons are released
  • These particles and photons are called rays
  • There are three kinds of rays produced by naturally occurring radioactivity

 a, b & g

a decay
a Decay
  • When a nucleus decays and emits a rays
  • a rays  ray of positively charged particles; He+2 nuclei  42He
  • AZP  A-4Z-2D + 42He

P  Parent

D  Daughter

a decay1
a Decay
  • Energy released = difference in beginning and ending total atomic mass units
  • 1 amu or u = 931.5 MeV
  • Since the parent and daughter nuclei are different this is a process called transmutation
b decay
b Decay
  • b rays consist of negatively charged particles
  • b– particles  electrons 0-1e
  • b- decay AZP  AZ+1D + 0-1e
  • b+ decay  AZP  AZ-1D + 01e (positron)
  • Use masses from Periodic Table to determine energy release
g decay
g Decay
  • The emission of high energy photons when a nucleus changes from an exited energy state(*) to a lower energy state
  • Does not cause a transmutation
  • AZP*  AZP + g
the neutrino
The Neutrino
  • Another particle emitted during b decay
  • Accounts for the energy missing from the KEb after emission
  • Verified experimentally in 1956
  • Has zero electric charge
  • Interacts weakly with matter
  • Has mass, a fraction of an electron’s, and travel at less than the speed of light