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Molecules E&R Chapter 12.

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Presentation on theme: "Molecules E&R Chapter 12."— Presentation transcript:

1 Molecules E&R Chapter 12

2 Outline Bonding 12-1 Molecular Excitations 12-4 Ionic 12-2
Covalent 12-3 Molecular Excitations 12-4 Rotation 12-5 Vibration 12-6 Electronic Electronic + Vibration + Rotation 12-7

3 Bonding R Nave, Georgia State Univ

4 Chemical Bonding R Nave, Georgia State Univ

5 Ionic Bonds RNave, GSU at

6 Ionic Bonds

7 Ionic Bonding RNave, Georgia State Univ at hyperphysics.phy-astr.gsu.edu/hbase/molecule

8 Ionic Bonding a.u. = atomic energy unit = 2*(13.6eV) Brandsen&Joachim

9 E&R

10 Covalent Bonds RNave, GSU at

11 Covalent Bonding SYM ASYM spatial spin ASYM SYM spatial spin

12 Covalent Bonding not really parallel, but spin-symmetric Stot = 1
not really anti, but spin-asym

13 Covalent Bonding Bransden&Joachin

14 Ionic vs Covalent Bond Properties
Ionic Characteristics Crystalline solids High melting & boiling point Conduct electricity when melted Many soluble in water, but not in non-polar liquids Covalent Characteristics Gases, liquids, non-crystalline solids Low melting & boiling point Poor conductors in all phases Many soluble in non-polar liquids but not water

15 Rotational Spectra w rotational A.M. moment of inertia

16 Rotation

17 Rotation

18 Rotational Spectra

19 Ocean Optics: Nitrogen N2
~ 0.3 eV ~ 0.4 eV

20 Vibration HF 970 HCl 480 HBr 410 Hi 320 CO 1860 NO 1530 “Spring Const”
Molecule “Spring Const” ( N/m ) HF 970 HCl 480 HBr 410 Hi 320 CO 1860 NO 1530

21 Vibration (in an Electronic state)

22 Electronic + Vibration

23 Electronic + Vibration + Rotation
2.550 eV 2.656 eV electronic excitation gap vibrational excitation gaps

24 Electronic + Vibration + Rotation
Vibrational Well Vibrational Well 2.656 eV depth ~ eV electronic excitation gap vibrational excitation gaps

25 Electronic, Vibration, Rotation
Electronic ~ optical & UV ~ 1 – 3 eV Vibration ~ IR ~ 10ths of eV Rotation ~ microwave ~ 1000ths of eV

26 Electronic + Vibration + Rotation
2.550 eV 2.656 eV electronic excitation gap vibrational excitation gaps

27 ** + Vibration + Rotation
IN A DIATOMIC MOLECULE because a photon has one unit of angular momentum, the rotational quantum number must change (vib is not angular motion) Dr = 0 not allowed

28 ** + Vibration + Rotation

29 Ocean Optics: Nitrogen N2
~ 0.3 eV ~ 0.4 eV

30

31 Some Molecular Constants
Molecule Equilibrium Distance Ro (Å) Dissociation NRG Do (eV) Vibrational freq v a (cm-1) Moment of Inertia Bb (cm-1) H2+ 1.06 2.65 2297 29.8 H2 0.742 4.48 4395 60.8 O2 1.21 5.08 1580 1.45 N2 1.09 9.75 2360 2.01 CO 1.13 9.60 2170 1.93 NO 1.15 5.3 1904 1.70 HCl 1.28 4.43 2990 10.6 NaCl 2.36 4.22 365 0.190 Notes: a) vibrational frequency in table is given as f / c b) moment of inertia in table is given as hbar2/(2I) / hc

32 Fluorescence absorb at one wavelength, emit at another

33 Phosphorescence tunneling slows the decay process


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