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. – 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 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 = E f - E i Simple equation for energies of light from H atoms. – Rydberg equation: 1/  = R(1/n f 2 - 1/n i 2 ), where R = a constant,  = observed wavelength, n f = integer (quantum number) representing the final energy level, n i = integer(quantum number) representing the initial energy level. n=1,2,3.... Do not need to know since just a special example of ∆E = E f -E i

Review First simple model Bohr model E n = -Rhc/n 2, – Rhc = x J/atom – note E < 0 – highest E-level is n= ∞  with E = 0 – Problem orbiting e- should fall into nucleus.

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) m l (magnetic QN) = 0, ±1,... ±l. m s =±1/2