Ch10 Nuclear Reactions and Half-life

Introduction to Nuclear Chemistry

Focus on nuclear reactions occurring in the nucleus of atoms.
Nuclear reactions differ from chemical reactions; they involve changes in the elements themselves.

Transmutation: The process where one element changes into another.
- Example: Polonium (Po) decays into Lead (Pb) via alpha decay.
- Nuclear reactions change the identity of elements.
Conservation of Mass in Reactions: Balancing mass numbers and atomic numbers.
- Example: Po-216 decaying results in:
  - Mass: 216 = 4 (alpha particle) + 212 (lead)
  - Atomic: 84 = 2 (alpha particle) + 82 (lead)
Half-life: The time it takes for half of a given substance to decay (e.g., Po has a half-life of 0.15 seconds).

Polonium emitting an alpha particle (2 protons, 2 neutrons).
Example with Uranium (U):
- U-238 decays, ejecting an alpha particle, transforming into Thorium (Th-234).
- Half-life of U-238: 4.5 billion years.

Thorium-234 emits a beta particle (similar to an electron).
A neutron transforms into a proton and the beta particle during decay.
Example:
- Balancing the equation for Th-234 decay:
  - Mass: 234 = 0 + 234; Atomic: 90 = -1 + 91 (becomes Protactinium-91).
- Th-234 has a half-life of 24 days, reducing quantity over time.

Positron: A positive electron emitted when a proton converts into a neutron and a positron.
Involves antimatter; annihilation with electrons produces energy (E=mc²).
Example: Potassium-40 decays to Argon-40 through positron emission, illustrated in balancing equations.

Iodine-131: Used in thyroid diagnostics, transforms into Xenon-131 with an 8-day half-life.
Iron: Evaluates anemia and blood production via radioactive labeling.
Krypton: A gamma emitter used for lung function tests by visualizing inhaled gas movements.

Splitting of heavy atoms (e.g., U-235) into lighter atoms and energy.
Needs enriched U-235 (from natural ratios, 0.7% fissionable).
Chain reactions sustain energy in nuclear power; chain reaction illustrated as ongoing splitting of U-235 begins with capturing a neutron.
Nuclear Power Plants: Utilize fission to generate heat and electricity via turbines.

Combining light nuclei (e.g., hydrogen isotopes) at high temperature to form heavier atoms (like helium).
Requires extreme conditions (~40,000,000 degrees) and has enormous energy output.
Benefits: Abundant fuel supply (hydrogen from oceans), potentially limitless clean energy.

Radioactive Waste: After intense fission, managing the alphabet soup of isotopes generated is complex and dangerous.
Safety and Risk: While nuclear power is efficient, concerns about accidents and long-term waste storage remain significant.

Nuclear chemistry involves understanding both nuclear and radiological processes.
Balancing equations, recognizing reaction types, and applying knowledge in practical scenarios, such as medicine and energy production, are vital.