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The Nucleus: A Chemist’s View. Nuclear Stability and Radioactive Thermodynamic stability - potential energy Kinetic stability - radioactive decay. Nuclide. A nuclide is a type of atom characterized by its proton number, neutron number and its energy condition.

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the nucleus a chemist s view
The Nucleus: A Chemist’s View

Nuclear Stability and Radioactive

  • Thermodynamic stability- potential energy
  • Kinetic stability-radioactive decay
nuclide
Nuclide
  • A nuclide is a type of atom characterized by its proton number, neutron number and its energy condition.
  • Nuclides with identical proton number but differing neutron number are called isotopes.
  • Conditions with a life of less than 10-10s are called excited conditions of a nuclide.
  • At present, more than 2,770 different nuclides are known, distributed over the 113 currently known elements, only 279 are stable with respect to radioactive decay.
known nuclides
Known nuclides
  • All nuclides with 84 or more protons are unstable with respect to radioactive decay.
  • Light nuclides are stable when (A-Z)/Z ratio is 1.
  • For heavier elements for stability, (A-Z)/Z ratio is greater than 1 and increases with Z.
slide5
Magic numbers: 2, 8, 20, 28, 50, 82, 126
  • Specific numbers of protons or neutrons produce especially stable nuclides.
types of radioactive decay a particle production
Types of Radioactive Decaya-particle production

The common modes of decay

  • Spontaneous fission
  • The splitting of a heavy nuclide into two lighter nuclides with similar mass numbers.
  • Slow rate for most nuclides
types of radioactive decay b particle production
Types of Radioactive Decayb-particle production

The common modes of decay

  • The net effect of b-particle production is to change a neutron to a proton.
  • The nuclides lie above the zone of stability.
  • The ratios of neutron/proton are too high.
types of radioactive decay g ray production
Types of Radioactive Decayg-ray production
  • high-energy photon
  • g-ray production accompanies unclear decays and particle reaction.
  • The emission of g rays is one way a nucleus with excess energy can relax to its ground state.
types of radioactive decay positron production
Types of Radioactive Decaypositron production
  • The net effect of this process is to change a e a protonto a neutron.
  • Higher neutron/proton ratio
  • Nuclides lie below the zone of stability.
antiparticle
Antiparticle

Matter-antimatter collisions, is called annihilation.

nuclear transformations
Nuclear Transformations
  • The conversion of one element into another
detection of radioactivity
Detection of Radioactivity

Geiger-Muller counter

drawbacks of radiocarbon dating
Drawbacks of Radiocarbon Dating
  • Errors up to 3000 years may have occurred. (Measurements of U/Th ratio development)
  • Large piece of the object must be burned.

(Use mass spectrometry)

figure 21 8 consumption of na 131 i
Figure 21.8: Consumption of Na131I

Source: Visuals Unlimited

energy for per nucleon
Energy for per Nucleon
  • The energy required to decompose this nucleus into its components has same numeric value but is positive.
  • This is called the binding energy per nucleon.
nuclear fission and nuclear fusion
Fusion: Combining two light nuclei to form a heavier, more stable nucleus.

Fission: Splitting a heavy nucleus into two nuclei with smaller mass numbers.

Nuclear Fission and Nuclear Fusion
chain reaction
Neutrons are also produced in the fission reactions.

Chain reaction-This makes it possible to produce a self-sustaining fission process.

Chain Reaction
subcritical
Subcritical
  • For the fission reaction, at least one neutron from each fission event must go on to split another nucleus.
  • Subcritical-If, on the average, less than one neutron causes another event, the process dies out.
critical
Critical
  • If exactly one neutron from each fission event causes another fission event, the process sustains itself at the same level.
supercritical
If more than one neutron from each fission event causes another fission event, the process rapidly escalates and the heat buildup causes a violent explosion.Supercritical
nuclear fusion
Nuclear Fusion
  • Bind two protons together.
  • A temperature of 4×107 K is required.
a schematic diagram of the tentative plan for deep underground isolation of nuclear waste
A schematic diagram of the tentative plan for deep underground isolation of nuclear waste.