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Announcements

Join the class today by activating your Clicker. Turn it on and press the "Join" button, followed by "20" and "Send" to confirm. Pick up a paper copy of the periodic table if needed. We will review the history of atomic models, including the early ideas of embedded electrons and Rutherford's dense nucleus concept. Understand why electrons don't fall into the nucleus due to quantized energy levels, supported by photon quantization evidence. Learn about key equations, like the Rydberg equation and Bohr model, as well as the Pauli Exclusion Principle in quantum mechanics.

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Announcements

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Presentation Transcript

  1. Announcements • To join clicker to class today: • Turn on the Clicker (the red LED comes on). • Push “Join” button followed by “20” followed by the “Send” button (switches to flashing green LED if successful). • Pick up paper copy of periodic table if you do not have text here or a table you can write on. Review • History of atomic models: • e- embedded in positive sphere (~1900) • Rutherford Experiment (1910) lead to idea of dense positively charged nucleus with e- somewhere outside

  2. Review • e- don’t fall into nucleus because trapped in “quantized” energy levels. • Evidence = quantization of light energy (photons, photoelectric effect) plus emission and absorption line spectra. • Can calculate energy of emission or absorption from ∆E = Ef-Ei • Simple equation for energies of light from H atoms. • Rydberg equation: 1/λ = R(1/nf2 - 1/ni2), • where R = a constant, λ = observed wavelength, nf = integer (quantum number) representing the final energy level, ni = integer(quantum number) representing the initial energy level. n=1,2,3.... • Do not need to know since just a special example of ∆E = Ef-Ei

  3. Review • First simple model Bohr model En = -Rhc/n2, • Rhc = 2.179 x 10-18 J/atom • note E < 0 • highest E-level is n= ∞with E = 0 • Problem orbiting e- should fall into nucleus.

  4. Quantum # Rules • Pauli Exclusion Principle: No two e- in the same atom may have all four quantum numbers the same. • n (principle) = 1, 2, 3 ...∞ (specifies shell) • l (angular momentum QN) = 0, 1, ...n -1 (0=s,1=p, 2=d, 3=f) • ml(magnetic QN) = 0, ±1, ... ±l. • ms=±1/2

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