3. Radioactivity Flashcards

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1
Q

Radioactivity facts

A
  • discovered by Becquerel in 1896
  • radiation given off by nucleus of unstable elements
  • radiation in form of particles or electromagnetic radiation
  • separates using magnetic field
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2
Q

Alphas

Betas

Gamma rays

A
  1. Are positive (curve path of travel field)
  2. Are negative (curved path in opposite direction)
  3. Have no charge (not affected by field)
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3
Q

Stable nucleons

Unstable nucleons

A

Potential barrier prevents nucleons entering/escaping nucleus
Nucleons posses kinetic energy

  1. Energy not sufficient to escape
  2. Nucleus has excess energy
    Constantly redistributed among nucleons
    Eventually one particle gains enough energy to escape
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4
Q

Decay constant

A
  • radioactive decay is statistical phenomenon
  • can not predict when a single atom will disintegrate
  • predict proportion of large collection that will decay in time t
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5
Q

Half life

A

Time required for activity of number of radioactive atoms to decay to 1/2 initial value

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6
Q

Radioactive series

A
  • first 92 elements in periodic table occur naturally
  • Z>92 elements produced artificially
  • elements with low Z tend to be stable, high Z is radioactive
  • as number of nucleons increases, nuclear forces become less effective
  • all elements with Z>82(lead) is radioactive
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7
Q

What are the naturally occurring radioactive elements?

A
  • uranium series
  • actinium series
  • thorium series
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8
Q

Alpha decay

A
  • typical of radioactive nuclides with very high Z (>82)
  • for Z >82, repulsion between protons overcomes nuclear forces
  • transformation characterized by emission of alpha particle
  • unstable nucleus emits particle of two protons and two neutrons
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9
Q

Beta and article decay

A
  • radioactive decay accompanied by ejection of positively or negatively charged electron ( positron or negatron)
  • neither particle exists in nucleus
  • creates at instant of decay process
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10
Q

Electron capture

A
  • electron capture is alternative process to beta plus decay
  • orbital electron captures by nucleus. Transforming proton into neutron
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11
Q

Internal conversion

A
  • ‘emission gamma’ is one mode by which an excited nucleus gets rid of excess energy
  • internal conversions is an alternative mode
  • excess nuclear energy passed to orbital electron (ejected)
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12
Q

The alpha, p reaction

A
  • first nuclear reaction was observed by Rutherford

- bombarded nitrogen gas with alpha particles(radioactive source)

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13
Q

The alpha, n reaction

A

-bombardment of nucleus by alpha particles with subsequent emission neutrons

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14
Q

Proton bombardment

A

-proton captured by nucleus with emission of gammas

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15
Q

Neutron bombardment

A
  • neutrons posses no electric charge
  • effective in penetrating nucleus and producing nuclear reactions
  • they do not have to posses high KE in order to penetrate nucleus
  • thermal neutrons extremely effective at producing transformations
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16
Q

Photodisintegration

A
  • nuclear reaction produced by interaction of high energy photon with nucleus
  • results in emission of neutrons
  • occurs for higher Z
17
Q

Fission

A
  • produced by bombarding high Z nuclei by neutrons

- after absorbing n. Nucleus splits into two nuclei of lower Z (plus extra neutrons)

18
Q

Nuclear reactors produce

A

Power

  • heat generated by absorbing gammas and neutrons
  • concerted to electric power

Radioisotopes

  • reactors provide large and continuous supple neutrons
  • necessary since probability of collusion low
  • used in medicine and research
19
Q

Fusion

A
  • reverse of nuclear fission
  • low mass nuclei combined to form one nucleus
  • total mass of products is less than the reactants
  • energy is released in the process