Untitled Notes

Exam and Course Updates

Practice Exam: A practice exam has been updated, including a key. Minor adjustments were made to the choices to ensure clarity. This information has been sent via Carmen email.
Exam Pickup: A reminder for students who have not picked up their exams that they should do so.

Demo Work: The class session will focus on "demo stuff," aiming to progress through the material. The intention is to understand key concepts, particularly regarding wave functions in molecular theories.
Feedback and Practice: Emphasized the advantage of the current material, which allows for greater practice and feedback compared to prior quantitative work.

Wave Functions: In discussing wave functions within Valence Bond Theory and Molecular Orbital Theory, it is emphasized that these functions are crucial for constructing a model of molecular interactions.
Hybridization: In organic chemistry, Valence Bond Theory is heavily utilized for understanding tetrahedral environments. It allows for the use of hybrid orbitals (s, p) to explain bonding. However, the addition of d orbitals is debated as being less useful due to their energy levels being too distant from s and p orbitals.
Limitations of VBT: The theory becomes less applicable when explaining molecules that require more than four domains (e.g., five or six hybridization) due to the unclear hybridization of d orbitals.

Introduction to MOT: The most complex and complete theoretical framework discussed, adequate for explaining phenomena that Valence Bond Theory cannot. Focus will be placed on applying this theory to homonuclear diatomics (e.g., $H2$, $He2$, $C2$, $N2$ including ions) up to neon.

Image Descriptions: Visual aids will illustrate how two hydrogen wave functions interact, both constructively and destructively. The constructive interaction leads to bonding molecular orbitals while destructive combines into antibonding orbitals, establishing nodes where no electron density is present.
Electron Density Distribution: Clarification of how electron density behaves in bonding versus antibonding situations. The bonding molecular orbital has lower energy and electron density concentrated between the two nuclei, while antibonding has higher energy and lacks this density.

Bonding vs. Antibonding: For hydrogen molecules, the bond order is calculated as follows: ext{Bond Order} = rac{1}{2} (Nb - Na) Where
- $N_b$ = Number of electrons in bonding orbitals
- $Na$ = Number of electrons in antibonding orbitals For $H2$:
- Bonding = 2, Antibonding = 0, leading to a bond order of 1 (indicating a single bond).

Resonance in Structures: Discusses how resonance structures can indicate different bonding states in compounds like benzene, allowing multiple valid structures through the movement of pi bonds and accounting for electron distribution across the molecule.

Magnetic Properties: The molecular orbital theory provides explanations for magnetic properties (e.g., whether a molecule is diamagnetic or paramagnetic). Oxygen ($O2$) is shown to be paramagnetic because of its unpaired electrons, while nitrogen ($N2$) is diamagnetic with all electrons paired.
Excited States: MOT allows for the exploration of excited states within molecules, akin to electron transitions in a hydrogen atom when photons interact.

Visualization of Hybrid Orbitals: Key insights into the shape and function of hybrid orbitals, the differences between sigma and pi bonds, and determining their phase match.
Complex Ordering of Orbitals: The arrangement of molecular orbitals varies slightly across the periodic table, with specific attention given to the ordering of orbitals, especially on the left versus the right side.

Real-World Applications: Recognition of how molecular orbital theory can be used beyond purely theoretical applications, with real-world examples of magnetic properties and bonding in molecular compounds.

Engage students in discussing concepts; ensure clarity on how wave functions impact bonding and the properties of atoms/molecules. Address whether molecular orbital theory enhances understanding compared to Lewis structures and Valence Bond Theory.