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)= * 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

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

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) !!!

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

Evolution of the atomic model so far…. Philosophical Magazine 44, 295 (1897) Philosophical Magazine Series 6, 21, (1911) Thomson Model 1897 Philosophical Magazine Series (1913) Bohr Model 1913

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

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

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

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

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…

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

Link to atomic line spectra of elements…none of which Bohr can explain except H

Evolution of the atomic model so far…. Philosophical Magazine 44, 295 (1897) Philosophical Magazine Series 6, 21, (1911) Thomson Model 1897 Philosophical Magazine Series (1913) Bohr Model 1913

“ 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’

The observed spectra define the energy levels in the elements

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

n= s p d The qualitative, general distribution of multi- electron atomic energy levels grouped by line type 4

n= s p d 4 p s d s s OBSERVED ATOMIC ENERGY LEVEL ORDERING SIMPLIFIED

n= 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

n= 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

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

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 Will stay in first 5 rows so f orbitals can be dropped H = 1s 1 He = Li= 2s 1 Be=1s 2 2s 2 + +

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 O F Ne 1s 2 2s 2 2p 4 1s 2 2s 2 2p 5 1s 2 2s 2 2p 6

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

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:

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

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

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)