Molecular Electronic Transitions that show Vibrational and Electronic Structure(Ch 20(983-985)

1. Molecular Electronic Transitions that show Vibrational and Electronic Structure(Ch 20(983-985) Molecule looks green IVR non-Radiative Transition Molecular Absorption Spectrum ISC singlet -Triplet Ch 6 6.0-6.10 (pg. 283) These transition are in theuv, visand near IR ISC (inter-system crossing internal energy transfer s=0 to s=1 ), IVR (internal vibrational Redistribution) of Energy in

2. 22s)nbpz)22(px)nb2(2py)nb nb-s* Fig. 6-20, p. 240

3. |b*|2 < |a*| Anti-bonding ~ a*1sH - b*2pz ||2=Probability Density |b|2 > |a|2 Bonding ~ a1sH + b2pz H F Fig. 6-21, p. 241

4. Robert Mulliken and Linus Pauling proposed a charge transfer model for the ionic contribution to polar bonds of heteronuclear diatomics.   Re(A-B) m= deRe Electric Dipole moment B A +e -e e is the partial charges transferred from the most electropositive atom(B) with Least EN to the more electronegative atom(A) with a larger EN. EN~(1/2){IE1 + EA} d ~ (|b|2 - |a|2) EN measures the relativity tendency of an electrons attraction to an atom: which d ~ (|b|2 - |a|2) is reflected in the fractional charge (d) on the atoms

5. Covalent Bond: No charge Transfer Partially Ionic Bond: Ionic Bond: almost complete charge Transfer Table 3-7, p. 106

6. Fig. 3-16, p. 107

7. E&Mwaves: The speed of light c = = 2.998 x108ms-1  wavelength units of nm=10-9 m and  Frequency Hz=s-1 Traveling wave Electric Field=Force per charge E=F/q, for a point charge

8. 3.0 2.5

9. I Infrared(IR) absorption for vibrational transitions only for molecules With dipole moments: Heteronuclear diatomics m= deRe Homonuclear diatomics: have no a dipole moment since d= 0 V(x) E2=5hw/2 E1=3hw/2 IR=hw hw E0=hw/2 - x + x 0 p. 102

10. Raman Scattering: hn + E0 E1 + hn ; E1–E0= (hn – hn)=hw~4000cm-1 (0 + ½)hw – (1 + ½)hw =hw~0.5 eV which also te difference between photon energies hn=2.5 eV hn= 3.0 eV Excited state Molecule E1 and scattered low energy photon Ground state Molecule E0 and Incident high energy photon Molecules with and With electric dipole moments p. 103

11. Lewis dot structure is a non-quantum mechanical way to determine bond order and to predict molecular stability using the Valence Electrons, non-Core Electrons, of the atoms in a molecule Valence Electrons H:(1s)  •H Li:1s22s2=Li[He]2s  •Li Core electrons Valence electrons p. 85

12. Chapter 3 and 6: The Octet Rule in Lewis Dot Structures Stable electronic configuration is for 1st row elements H is that of He Stable electronic configuration for 2nd and 3rd row elements is that of Ne and Ar respectively, 8 electrons in the filled ns + np sub-shells The origin of the so called “Octet Rule” used in Lewis Dot structures Form bonds by losing, gaining or sharing to form a rear configuration p. 85

13. In the Lewis dot structure of H-Cl the bonding pair corresponds the s bonding MO and the non-bonding lone pairs in the snb(2sCl) MO and the degenerate non-bonding πx/y electrons on the Cl atom p. 85

14. sp- sp+ Fig. 6-15, p. 235

15. Z=7 Z=9 N2 F2 Unhybridized Z >7 spHybridized Z ≤7 Less overlap higher energy due to s-p Hybridization More overlap Lower Energy Fig. 6-16, p. 236

16. Lewis Dot Structure vs VB(Localized electrons) & MO(delecalized electrons) Theories O:(He)2s22p4; 6 Valence Electrons atom, so 12 total 2s)2s)pz)2(2px)2(2py)(2px) (2py) p. 235

17. Lewis Dot Structure vs VB(Localized electrons) & MO(delecalized electrons) Theories O:(He)2s22p4; 6 Valence Electrons atom, so 12 total 2s)2s)pz)2(2px)2(2py)(2px) (2py) (Paramagnetic) (Diamagnetic) p. 235

18. O2 is paramagnetic, ground state is a triplet Lewis Structure predicts Diamagnetism Fig. 6-17a, p. 237

19. Chap 5: Photoelectron Spectroscopy is to measure the one electron Orbital Energies h Energy (nl) of a Hartree Orbital One electron hydrogen like orbital nlmr is, approximately the Electron’s ionization energy IEnl This is the so called “Koopmans’ approximation” Stated more precisely: IEnl= - nl NeNe+ + e E=IE~ - nl KE 2p 2s Therefore a measurement of IEnl is the same as measuring nl KE= (1/2)mev2 = h- IEnl 1s Orbital Energies for Ne

20. Chap 6: Molecular Photoelectron Spectroscopy (PES) n = vibrational quantum number 2 3 20 1 4 5 0 D0 ~ 2.3 eV 10 6 8 10 5 14 0 KE -IE H2+ hH+2 + e

21. Chap 6: Molecular Photoelectron Spectroscopy KEn= h - IE fastest electrons KEn= h - IE - 2 Slowest for n> 2 even Slower KEn= h - IE - n where n= nh H+2 + e(Ken) R(H + H+) 2 Ground state of H2+ of the ion 1 0 R(H + H) Re(H+2) IE Ground state of Neutral H2 Re(H2)

22. Photoelectron spectroscopy (PES) of H2 KE2=(h-IE)-2h KE1=(h-IE)-h KE0=(h-IE) h H+2(1g) + e 1u H+ H 1g H2(1g) 1g

23. Chap 6: Molecular Photoelectron Spectroscopy (PES) i

24. HCl Fig. 6-31, p. 249

25. 22s)nbpz)22(px)nb2(2py)nb Fig. 6-20, p. 240

26. H HCl Cl 23s)nbpz)22(3px)nb2(3py)nb Fig. 6-20, p. 240

27. Chap 6: PES of HCl:2s)sH-pClz)2(3px) 2(3py) HCl photoelectron Spectra

28. N2 F2 S-P Hybridization Z ≤7 Less overlap due s-p Hybridization Fig. 6-16, p. 236

29. N2 F2 S-P Hybridization Z ≤7 HOMO: (2pz) Highest Occupied MO LUMO: * Lowest Unoccupied MO

30. N:(He)2s22p3; N2: 22s) 22s)2(2px)2(2py)pz) N2 O:(He)2s22p4; 2s)2s)pz)2(2px)2(2py)(2px) (2py) Hund’s Rule O2

31. Chap 6: Molecular Photoelectron Spectroscopy (PES) NO O:(He)2s22p4; N:(He)2s22p3 2s)2s))2(2px)2(2py)pz) (2px)/(2py)