Introduction to Nuclear Interactions

Strong Nuclear Force: Acts when two nuclei approach, leading to a decrease in potential energy.Coulombic Barrier: Two protons are initially repelled due to electrostatic forces; this increases potential energy.Energy Requirement: High energy input is needed to overcome the Coulombic barrier for nuclear fusion.

Potential Energy Diagram of Protons

• Start with protons far apart on the x-axis.

• As they come closer, potential energy starts low, rises due to repulsion, and then drops sharply as they are pulled together by the strong nuclear force.

• Correct representation is found in diagram C from the worksheet.

Nuclear Fusion Energy Release

• Fusion of nuclei leads to a significant energy release that is comparable to bond formation in chemical reactions.

• Example: Fusing deuterium and tritium results in helium, a neutron, and lots of energy.

• E=mc² Relation: Introduces mass-energy equivalence; mass lost in reactions is converted into energy.

Binding Energy and Mass Defect

• Mass Defect: The difference in mass between bound nucleons and individual nucleons, leading to energy release.

• Calculated using: Mass (in kg or amu) converted to energy via Einstein’s equation.

• Binding energy quantifies energy released when nucleons form a nucleus.

Practice Problems

• Deuterium Atom Energy Release: Calculated energy released when one deuterium atom is formed.

• Result: 3.56 x 10⁻¹³ Joules.

• One Mole of Deuterium: Energy per mole calculated as 2.14 x 10¹¹ Joules.

• Comparison: Fusion releases significantly more energy than combustion (240,000 times more).

Nuclear Reactions Overview

• Fusion vs. Fission:

  • Fusion: Light nuclei combine into heavier nuclei, releasing substantial energy.

  • Fission: Heavy nuclei split into lighter, more stable nuclei, also releasing energy.

• Deuterium and Tritium: Fusion of these isotopes yields energy and is fundamental in stellar processes.

Fusion in Stars

• Hydrogen Burning: Four protons fuse into a single helium nucleus; an example of fusion in stars.

• The process reduces the total number of nucleons in the universe over time.

• Stellar dynamics lead to the formation of heavier atoms beyond hydrogen, helium, and lithium.

Radioactive Decay

• Types of Decay: Includes alpha decay (He nucleus emitted), beta decay (electron emitted), positron emission, electron capture, and gamma radiation.

• Stability Factors: Neutron-proton ratios define stability; heavier elements favor more neutrons.

Atomic Interactions and Properties

• Emergent Properties: Properties of materials arise from atomic interactions, e.g. phase changes, boiling points, etc.

• Phase Changes: Energy is absorbed (endothermic) to overcome intermolecular forces during melting/boiling.

• Chemical Bonds: Include covalent bonds (strong, between nonmetals) and metallic bonds (in metals).

Potential Energy Curves

• Attractive vs. Repulsive Forces: Determine the stability of molecular interactions.

• Bond Formation: Involves overcoming a potential energy barrier and results in energy release as molecular structures form.

Valence Bond Theory vs. Molecular Orbital Theory

• Valence Bond Theory: Bonds form via overlapping atomic orbitals; electrons are localized.

• Molecular Orbital Theory: Atomic orbitals combine to create bonding and antibonding orbitals, treating electrons as delocalized.

Properties of Metals vs. Nonmetals

• Metal Characteristics: Malleability, ductility, conductivity due to free-moving electrons in overlapping orbitals.

• Appearance: Shiny due to photon interactions with metallic bonding.

• Electrons in Metals: Can move freely, giving rise to conductivity and sheen.

Allotropes of Carbon

• Graphite vs. Diamond: Differences attributed to bonding structure.

• Diamond: 3D network of strong covalent bonds resulting in high hardness; does not conduct electricity due to localized electrons.

• Graphite: Layered structure allows for conduction of electricity via delocalized pi bonding within and between layers, making it soft and slippery. Additionally, the layers can slide over each other easily, explaining graphite's lubricating properties. Graphite's layers also contribute to its high melting point as breaking the bonds requires significant energy. This is why diamonds are used in cutting tools while graphite is often used in lubricants and batteries.