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Quantum Chemistry
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Chemistry Connections
Quantum Chemistry
Episode #7
Welcome to Chemistry Connections, my name is Owen Mahan and I am your host for episode #7 called Quantum Chemistry. Today I will be discussing how the effects of quantum mechanics lead to chemistry.
Segment 1: Introduction to Quantum Mechanics
- Quantum mechanics is the mechanism behind the world on the smallest scale
- QM acts on the smallest scale, classical mechanics on our scale, relativity on a large scale
- Quantum comes from the fact that things are quantized
- Energy, charge, etc can only have certain integer multiples of quantities
- Schrodinger equation (or the wave function) means the values of quantum systems are only probabilistic
- Heisenberg uncertainty principle means you can’t know everything about a system
- Pauli exclusion principle says that multiple of the same fermion can’t exist at the same time
- Fermions have ½ integer spin (electrons, quarks, nucleons by extension, etc) while bosons have whole integer spin (photons, gluons, etc)
Segment 2: Quantum Effects on Chemistry
- Bonding/Potential Energy
- All chemical interactions are based on quantum mechanics
- Bonding occurs because of low potential energy states and electron clouds form because of that
- Metallic bonding was used to discover QM via photoelectric effect (Einstein)
- A solution to the schrodinger equation using Born-Oppenheimer methods is what gives the energy vs nuclear distance graph (as seen on the AP exam)
- Overlapping is the process by which electron clouds enter a newly favorable state as atoms bond
- Resonance structures are superpositions of electrons within molecules which create multiple simultaneous overlapping cloud structures
- Orbitals occur because of spin mechanics as ½ spin particles cannot be indistinguishable, so a max of two electrons (½ and -½ spin respectively) can occupy an orbital
- Helium superfluid occurs because He-4 atoms have 0 combined spin so can fall into the same states
- Neutron stars (the densest things in the universe) occur because the pressure of fermions not wanting to occupy the same state barely overcomes the gravitational pressure
- Entropy - 34 min
- Entropy can be thought of as an effect of quantum mechanics
- The potential number of states determines the entropy of a system
- A system seemingly in perfect order at a moment in time can still have the same entropy as a “disordered” permutation of the same system
- Gas mixtures can at one point be perfectly separated but if it is not locked into that state it has the same entropy as any mixed state of the same system
- It is the information “hidden” by the system, called Von Neumann entropy
- Interesting applications include black holes, as information is seemingly lost
- Resolved by the idea that entropy is hidden information on the surface area of the black hole which is released via Hawking radiation
Segment 3: Personal Connections
- Fundamental physics is the most important branch of science to pushing technology forward
- Relates to literally all other fields of science
- I find it very interesting because there is so much depth you can go into
- Explains questions about other fields
- Quantum chemistry is especially interesting because being able to understand what creates chemical phenomena allows for a better understanding of the phenomena themselves
Thank you for listening to this episode of Chemistry Connections. For more student-ran podcasts and digital content, make sure that you visit www.hvspn.com.
Sources:
https://www.sciencedirect.com/topics/earth-and-planetary-sciences/photoelectric-effect
Music Credits
Warm Nights by @LakeyInspired
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