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Chemistry ELECTRONIC STRUCTURE The quantum mechanical model

Chemistry ELECTRONIC STRUCTURE The quantum mechanical model. DO NOW: TAKE out homework to check Calculators REQUIRED Periodic tables not required. Problems With the Bohr Model.

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Chemistry ELECTRONIC STRUCTURE The quantum mechanical model

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  1. ChemistryELECTRONIC STRUCTUREThe quantum mechanical model DO NOW: TAKE out homework to check Calculators REQUIRED Periodic tables not required

  2. Problems With the Bohr Model • For a one-electron hydrogen atom, all electrons on the same energy level have the same energy, so thinking only about energy levels worked for hydrogen, but did not explain other elements’ emission spectra.

  3. Energies of Orbitals • As the number of electrons increases, though, so does the repulsion between them, creating splits in the energy levels. • A new, mathematical model of the atom resulted to explain this phenomenon.

  4. Scientists’ Contributions • Louis de Broglie observed that just like light can behave like a particle, particles could behave like waves, so electrons could have wave-like properties. • Werner Heisenberg showed that you can not know exactly where an electron is in an atom due to this “quantum weirdness” – you can just know an area where an electron is likely to be at any given point. • Called the Heisenberg uncertainty principle • These areas are known as orbitals, and they are 3-D mathematical graphs that show regions of space where electrons are likely to be. • Orbitals are also called “electron clouds” and where the cloud is most dense, the more likely an electron is in that region.

  5. A Word on ORBITALS • (This is not notes) • Orbital theory provides information about electrons in the atom. Orbitals are graphed solutions of Schrodinger’s equation, which is not solvable until college-level physical chemistry. You have to just accept that these orbitals have these shapes and follow these rules.

  6. Pauli Exclusion Principle • No two electrons may have the same energy in an atom. • If they have the same energy, they are theoretically identical, which is forbidden according to quantum theory. • So, every electron in an atom MUST BE DOING SOMETHING DIFFERENT. Ways an electron can be different: • Its energy level (from the Bohr model) • Its shape of orbital • The orbitals’ position in space • The direction an electron is spinning

  7. s Orbitals • They are spherical in shape. • The radius of the sphere increases with the value of n, the energy level of the atom. • There is only one s orbital per energy level.

  8. p Orbitals • There are 3 p orbitals in each energy level, n = 2 and beyond. • They have two lobes with a node between them. • (They look like hourglasses)

  9. d Orbitals • There are 5 dorbitals in each energy level, n = 3and beyond. • They resemble 4-leaf clovers.

  10. FOrbitals • There are 7forbitals in each energy level, n = 4and beyond. • They have more obscure shapes.

  11. Some Vocab • The value of n (energy level) is sometimes called a shell or level. • Orbital shapes (s, p, d, f) are called subshells or sublevel.

  12. ORBITAL SUMMARY • Confused yet? Here is a summary of energy levels and orbitals: • Remember for tomorrow – each electron must be doing something different!

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