1. From pure theory Bohr derives the Energy, E H, of the electron around Hydrogen and proposes the Bohr model of the atom: E H (J)= -2.178*10 -18 n 2 n=3 n=2 n=1 n=1,2,3…are integers defining circular orbits around positive nucleus Eq. 2.1 of text

2. Bohr Model Predictions vs. Experiment n= 5 4 3 2 1 5  2 = 435 486 656 nm Observed H line (sun) spectrum (Balmer series) Bohr’s `explanation of H spectrum’: quantum transitions between levels obs 435 486 656 4242 3  2 n i n f 5 2 4 2 3 2 Calc theory 435 486 656 0 % error between observed and calculated !!!

3. Theoretical Computed radius of first H orbit: Bohr Model Predictions vs. Experiment (continued) Experimentally measured ground state radius of H: 5.20 nm 0 % error between observed and calculated (again) !!!

4. Let’s confirm that n=5  n=2 electron jump predicts =434.9 nm for H using Bohr model: h=6.63*10 -34 J s c=3*10 8 m/s h*c= 1.989*10 -25 J*m E 5 –E 2 =  E= hc

5. Evolution of the atomic model so far…. Philosophical Magazine 44, 295 (1897) Philosophical Magazine Series 6, 21, 669-688 (1911) Thomson Model 1897 Philosophical Magazine Series 6 26. 1-25 (1913) Bohr Model 1913

6. the quantum cat dilemma-one consequence of Bohr’s quantum concept Kitty state =  = f 1  1 f 2  2 (According to quantum physics) f 1 ~ 1, but not quitef 2 ~ 0 but not quite

7. Another animated, Abused quantum cat-in-a-box story….

8. Walter White talking chemistry in “Breaking Bad” What happened to chemistry ?????

9. The experimental chemists and spectroscopists say “fugetabout” it. “ typical” experimental spectroscopist/chemist 1930 Bohr theor y Experimentalist’s attitude towards theoreticians: “ If I want your opinion, I’ll give it to you…” The Bohr Model dies…1930

10. 1)Bohr can’t predict anything right except H. The other elements have too many lines, e.g. Na BOHR 1 line predicted 1  11 Bohr’s prediction: 1 green line EXPERIMENT 11 LINES OBSERVED Observed Na-`D’ line Is yellow Even worse.. Spectroscopists observe…. 11 lines !! 1930 Bohr theory Bohr’s little Problem…

11. Bohr model’s failures (continued) Can’t predict magnetic `fine’ structure of H, e.g … magnetize H and even n=1 splits into 2 lines Turn on magnet near H 1  21  2  Not even the smartest theoretical physicists of the day (Sommerfeld, Planck, Dirac) can make 1=2 or 1=11…. with Bohr’s model 2 )… even Bohr’s predictions for H have problems

12. Link to atomic line spectra of elements…none of which Bohr can explain except H http://chemistry.bd.psu.edu/jircitano/periodic4.html

13. Evolution of the atomic model so far…. Philosophical Magazine 44, 295 (1897) Philosophical Magazine Series 6, 21, 669-688 (1911) Thomson Model 1897 Philosophical Magazine Series 6 26. 1-25 (1913) Bohr Model 1913

14. “ Model 4: The spectroscopist’s atom … or why we sing the spdf song My way or the highway… The spectroscopists description of what they deduce from observing lines is the `atom’

15. The observed spectra define the energy levels in the elements

16. Four main `line’ types are observed in atomic spectra: 1.Sharp lines (=> very narrow) 2. Principal lines (=> most intense) 3. Diffuse lines (=> weak, broad ) 4. Fundamental lines (=> family of lines terminating spectra at high energy) abbreviations s p d f

17. n=1 2 3 4 5 3 2 3 4 s p d The qualitative, general distribution of multi- electron atomic energy levels grouped by line type 4

18. n=1 5 3 2 3 4 s p d 4 p s d s s OBSERVED ATOMIC ENERGY LEVEL ORDERING SIMPLIFIED

19. n=1 5 3 2 3 4 s p d 4 p s d s s Describing Carbon’s energy levels C has 6 electrons C=1s 2 2s 2 2p 2

20. n=1 5 3 2 3 4 s p d 4 p s d s s Describing Fluorine’s energy levels F has 9 electrons F=1s 2 2s 2 2p 5

21. How to sing the spdf song without memorizing the energy levels: electron neighborhoods: s, p, d and f s p d 12345671234567 f 3d 4d 5d 6d 4f 5f

22. Singing the song…what is the complete electronic configuration of…. 1s 2 1s 2 2s 1 1s 2 s d p f 3d 4d 5d 6d 12345671234567 Will stay in first 5 rows so f orbitals can be dropped H = 1s 1 He = Li= 2s 1 Be=1s 2 2s 2 + +

23. spdf song –continued: YOU complete electronic configuration of: H He Li Be B C N 1s 1 1s 2 1s 2 2s 1 1s 2 2s 2 1s 2 2s 2 2p 1 1s 2 2s 2 2p 3 1s 2 2s 2 2p 2 sdpsdp 1234512345 O F Ne 1s 2 2s 2 2p 4 1s 2 2s 2 2p 5 1s 2 2s 2 2p 6

24. sdpsdp 3d 4d 5d 6d He is s not p IN-CLASS EXERCISE : COMPLETE ELECTRONIC CONFIGURATIONS

25. a)Cl b)K c) Mn d ) Se 1s 2 2s 2 2p 6 3s 2 3p 5 1s 2 2s 2 2p 6 3s 2 3p 6 4s 1 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 5 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 4 Write complete electronic configurations for:

26. 2.2 Write the abbreviated electron configurations for the elements below, assuming they are in the gas phase. a) Ca b) Al c) As [ Ar] 4s 2 [ Ne] 3s 2 3p 1 [Ar] 4s 2 3d 10 4p 3

27. d electron variations Mn 1) s d electron configuration switching [Ar] 4s 2 3d 5 [Ar] 3d 5 4s 2 [Ar] 3d 5 From spectra of atomized elements As it behaves chemically in solution Mn 2+ Evidenced by fact that all transition metals have a stable 2+ state… => outer 4s 2 are removed first Example: behavior of Mn

28. 2.3. Write the correct, abbreviated d-switched configurations for the transition metals below a ) Cu b) Fe 2+ c) Zn 2+ [Ar] 3d 9 4s 2 (3d and 4s switch order) [Ar] 3d 6 (outer 4s electrons lost first) [Ar] 3d 10 (outer 4s electrons lost first)