Nuclear Chemistry Notes

Here are more detailed explanations for the content on the left-hand side (LHS) under each heading:

Nuclear Chemistry

Definition: Nuclear chemistry involves reactions with nuclear changes, not standard chemical reactions.
Element Transformation: Atoms of one element are transformed into another element.
Particle Involvement: Nucleons (protons and neutrons) are directly involved, unlike typical chemical reactions that only involve electrons.
Energy Change: Small changes in mass result in large changes in energy, described by $\Delta E = \Delta mc^2$
Rate Factors: Reaction rates depend on the amount of substance (moles) and are not influenced by temperature or catalysts.

Einstein's Equation and Binding Energy

Link to Physics: Nuclear chemistry links chemistry and physics.
Nuclear Forces: Forces hold the nucleus together; the energy required to break it apart is the binding energy.
Binding Energy (BE) Defined: $BE = \Delta mc^2$
Nuclide Definition: A nuclide refers to a specific atom with a particular isotopic composition.
Nuclide Stability: Nuclides are either stable or unstable, depending on their binding energy per nucleon.

Binding Energy vs. Nuclear Stability

Stability Correlation: Greater released binding energy per nucleon indicates a more stable nuclide.
Maximum Stability: Iron-56 ( $^{56}Fe$ ) exhibits the highest nuclear stability.
Fission Tendency: Nuclides heavier than iron-56 typically undergo fission to achieve smaller sizes and greater stability.
Fusion Tendency: Nuclides lighter than iron-56 tend to undergo fusion to form larger, more stable nuclei.

Nuclear Reactions

Reaction Nature: Nuclear reactions occur both naturally and through human intervention, shifting the nucleus toward a stable neutron-to-proton (N:Z) ratio.
Kinetic Stability: Kinetic stability is quantified as the probability of radioactive decay.
Radioactive Decay Example: $\^{14}_6C \rightarrow \ ^{14}_7N + \ ^{0}_-1e$ describes carbon-14 decaying into nitrogen-14, emitting a beta particle.
High-Energy Electron: The emitted $^{0}_-1e$ represents a high-energy electron.
Conservation Laws: Mass number (A) and atomic number (Z) are conserved in nuclear reactions.

Alpha Decay Example

Radium-226 Decay: Alpha decay of Radium-226 into Radon-222 is shown by: $^{226}_88Ra \rightarrow \ ^{222}_86Rn + \ ^{4}_2He$
Mass Number Conservation: $226 = 222 + 4$ , illustrating that the total mass number remains constant.
Atomic Number Conservation: $88 = 86 + 2$ , confirming the atomic number's conservation.

Radioactive Elements

Radiocarbon Properties: Radiocarbon ( $^{14}_6C$ ) is a radioisotope characterized by a half-life of 5715 years.
Stable Isotope: Carbon ( $^{12}_6C$ ) is a stable isotope, unlike radiocarbon.
Nuclide Stability Statistics: Of approximately 2000 known nuclides, only 279 are kinetically stable, while the rest are radioactive.
Zone of Stability: Within this zone, the strong nuclear force is nearly equivalent to the electrostatic force.
Alpha Emission: Nuclides with Z > 84 are radioactive and primarily decay through alpha emission.

Nuclear Reactions and High Energy Radiation

Radiation Emission: Nuclear reactions often emit high-energy radiation.
Energy-Wavelength Relation: The relationship between energy and wavelength is $E = \frac{hc}{\lambda}$ , where h is Planck's constant, and c is the speed of light.
Energy and Wavelength: Shorter wavelengths correspond to higher energy levels.
Radiation Types: Gamma rays are highly energetic; radio waves are not.
Spontaneous Decomposition: Unstable nuclides undergo spontaneous decomposition, releasing particles or energy.

Ionising Radiation

Types of Radiation: Ionising radiation includes alpha ( $\alpha$ ), beta ( $\beta$ ), and gamma ( $\gamma$ ) radiation.
Ionization Process: This radiation has enough energy to cause atoms to become ions.
Alpha Particle Characteristics: Alpha particles have a short range (e.g., 60 \(\mu $m in lungs) and cause significant internal damage, especially from alpha-emitting Radon-222.</li><li>Beta/Gamma Penetration: Beta particles and gamma rays have longer ranges and can penetrate the skin (e.g., Strontium-90), making them more hazardous.</li><li>Therapeutic Uses: Applications include Positron Emission Tomography (PET) using FDG to image metabolic processes like brain function and tumor formation.</li></ul>Radioactive Decay - Alpha<ul><li>Alpha Decay Process: Emission of an alpha particle ($ \ ^{4}_2He $or$ \ ^{4}_2He^{2+} $).</li><li>Example Reaction:$ \^{226}_88Ra \rightarrow \ ^{222}_86Rn + \ ^{4}_2He $</li><li>Radium Properties: Radium is a high-activity alpha emitter.</li><li>N:Z Ratio Effect: Increases the neutron-to-proton ratio in nuclei with too many protons.</li><li>Particle Emission: Involves the ejection of particles in both alpha and beta decay.</li></ul>Radioactive Decay - Beta<ul><li>Beta Decay Process: Emission of a high-speed electron ($ \ ^{0}_-1e $) from the nucleus.</li><li>Neutron Transformation: A neutron converts into an electron and a proton:$ \^{1}_0n \rightarrow \ ^{0}_-1e + \ ^{1}_1p $</li><li>Example Reaction:$ \^{14}_6C \rightarrow \ ^{14}_7N + \ ^{0}_-1e $</li><li>Radiocarbon Properties: Radiocarbon is a low-activity beta emitter.</li><li>N:Z Ratio Effect: Decreases the neutron-to-proton ratio in nuclei with too many neutrons.</li></ul>Radioactive Decay - Gamma<ul><li>Gamma Decay Process: Emission of a gamma photon ($ \ ^{0}_0\gamma $), which is high-energy electromagnetic radiation.</li><li>Example Reaction:$ \^{238}_92U \rightarrow \ ^{234}_90Th + \ ^{4}_2He + 2 \ ^{0}_0\gamma
Uranium Properties: Uranium-238 is an alpha and gamma emitter with low activity; Uranium-235 is used in the nuclear industry.
Isotope Change: Gamma emission alone does not change the isotope or element.
Energy Release: Gamma decay releases energy as electromagnetic radiation.

Radiation Characteristics

Alpha Particles:
- Physical Properties: Relatively large, heavy, and doubly charged.
- Penetration: Low penetration depth due to quick energy loss in matter.
- Shielding: Easily shielded by materials like paper or skin.
Beta Particles:
- Physical Properties: Much smaller and singly charged.
- Penetration: Higher penetration capability compared to alpha particles due to higher speed.
- Shielding: Shielded by thin, low-density materials, such as a few millimeters of plastic.
Gamma Rays & X-rays:
- Physical Properties: High-energy electromagnetic radiation.
- Penetration: Very high penetration capability.
- Shielding: Requires thick, dense materials like lead for effective shielding.

Decay Series

Decay Sequence: Radioactive elements (radionuclides) undergo a series of decays until they reach a stable nuclide.
Nuclide Roles: The starting element is the parent nuclide, and the resulting element is the daughter nuclide.
Example Series: Uranium-238 (\ ^{238}_92U $) decays to Lead-206 ($ \ ^{206}_82Pb $) with a half-life of 4.51e9 years.</li></ul>Half-Lives I<ul><li>Definition: Half-life is the duration it takes for half of the parent isotope in a sample to decay.</li><li>Half-Life Symbol: Expressed as$ t_{1/2} $, it is the time for half the mass or moles of a substance to decay.</li><li>Example: The time for 1 g of a substance to decay to 0.5 g is equal to one half-life.</li></ul>Radio-Activity<ul><li>Measurement Unit: Radioactivity is measured in Becquerels (Bq), where 1 Bq = 1 decay per second.</li><li>Unit Origin: The SI unit used in Australia, named after Henri Becquerel.</li><li>Activity Factors: Depends on the decay rate ($ t_{1/2} $) and the quantity of the radioactive material (moles).</li></ul>Half-Lives II<ul><li>Instability: Shorter half-lives indicate greater instability of the radionuclide.</li><li>Half-Life Constancy: The half-life of a given radionuclide is constant.</li><li>Decay Independence: The decay rate is not affected by temperature or the amount of radioactive nuclei.</li><li>Example Calculation: Demonstrates calculating the remaining activity of Cobalt-60 over three half-life intervals, reducing from 800 Bq to 100 Bq over 15 years.</li></ul>Curie<ul><li>Definition: The Curie (Ci) is a non-SI unit representing the number of decay events in 1 gram of Radium-226 ($ \ ^{226}Ra $).</li><li>Curie Conversion: 1 Ci equals$ 3 x 10^{10} $Bq.</li><li>Usage: The typical US unit is the picoCurie (pCi), equivalent to$ 10^{-12}$$ Ci.
Historical Context: Named after Marie and Pierre Curie; Marie Curie was a Nobel laureate in both Physics and Chemistry and died from aplastic anemia due to radiation exposure.