Announcements

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