Physical Chemistry 2019/4/6 复旦大学化学系.

Presentation on theme: "Physical Chemistry 2019/4/6 复旦大学化学系."— Presentation transcript:

1 Physical Chemistry 2019/4/6 复旦大学化学系

2 I try to do my best each day, In my work and in my play;
Children’s Song I try to do my best each day, In my work and in my play; And if I always do my best, I need not care about the test. 2019/4/6 复旦大学化学系

3 Molecular Structure and Bonding
Chapter Three Molecular Structure and Bonding The force of attraction between two atoms or ions that hold them together in a unit is called Chemical Bond What is the nature of Chemical Bond? ----The History Ideas 2019/4/6 复旦大学化学系

4 3-1 Covalence bond Theory
W.Kossel : one or more electrons from one atom are removed and attached to another atom, resulting in positive and negative ions which attract each other----ionic binding G.W.Lewis: one or more pairs of electrons are shared by two atoms covalent binding G.W.Lewis 2019/4/6 复旦大学化学系

5 3-1 Covalence bond Theory
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6 3-1 Covalence bond Theory Covalent and Ionic Binding
Contour maps of the molecular charge distributions of N2 and LiF at their equilibrium internuclear separations 2019/4/6 复旦大学化学系

7 3-1 Covalence bond Theory
The Hamiltonian of H2 is The underlying physical laws necessary for the mathematical theory of … the whole of chemistry are thus completely known, and the difficulty is only that the exact application of these laws leads to equations much too complicated to be soluble. Dirac 2019/4/6 复旦大学化学系

8 3-1 Covalence bond Theory
B.O. Approximation a b 1 2 Oppenheimei 2019/4/6 复旦大学化学系

9 3-1 Covalence bond Theory
Separate Variables W.Heitler and F.London’s contribution 2019/4/6 复旦大学化学系

10 3-1 Covalence bond Theory
Linear Variational Method Trial Eigenfunction 2019/4/6 复旦大学化学系

11 3-1 Covalence bond Theory
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12 3-1 Covalence bond Theory
Linear homogeneous equations Secular determinant 2019/4/6 复旦大学化学系

13 3-1 Covalence bond Theory
Problem: Carry out a linear variation calculation for a particle of mass m in one-dimensional infinite potential well of width l. Use and as trial eigenfunction. Compare the result with the exact ground- state energy. 2019/4/6 复旦大学化学系

14 3-1 Covalence bond Theory
overlap 2019/4/6 复旦大学化学系

15 3-1 Covalence bond Theory
Heitler-London Shoujing Wang 王守竟 2019/4/6 复旦大学化学系

16 3-1 Covalence bond Theory
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17 3-1 Covalence bond Theory
W.Kolos C.C.Roothaan 2019/4/6 复旦大学化学系

18 3-1 Covalence bond Theory
Electronic Structure Bonding Anti-bonding 2019/4/6 复旦大学化学系

19 3-1 Covalence bond Theory The Nature of the Covalent Bond
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20 3-1 Covalence bond Theory
A contour map of the electron density distribution (or the molecular charge distribution) for H2 in a plane containing the nuclei. Also shown is a profile of the density distribution along the internuclear axis. The internuclear separation is 1.4 au. The values of the contours increase in magnitude from the outermost one inwards towards the nuclei. The values of the contours in this and all succeeding diagrams are given in au; 1 au = e/ao3 = e/Å3. 2019/4/6 复旦大学化学系

21 3-1 Covalence bond Theory
A series of electron density contour maps illustrating the changes in the electron charge distribution during the approach of two H atoms to form H2. The internuclear distance R in units of au is indicated beneath each map. 2019/4/6 复旦大学化学系

22 3-1 Covalence bond Theory
Density difference distribution (molecular minus atomic) for the approach of two H atoms. These maps indicate the changes in the atomic densities caused by the formation of a molecule. 2019/4/6 复旦大学化学系

23 3-1 Covalence bond Theory
The spin of electron 2019/4/6 复旦大学化学系

24 3-1 Covalence bond Theory
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25 3-1 Covalence bond Theory
Summary of Valence Bond Theory and Its Application 1. These two electrons must have opposite spins. 2. Principle of Maximum Overlap: the strength of the bond depends on the extent of overlap of the charge clouds on the two atoms. 2019/4/6 复旦大学化学系

26 3-1 Covalence bond Theory
The Application for Some Molecules Li2 He2 N2 HF CO H+2 O2 H2O N N 2019/4/6 复旦大学化学系

27 3-2 Molecular Orbital Theory
The Hamiltonian for H2+ in atomic unit L.C.Pauling B.O. Approximation a b 2019/4/6 复旦大学化学系

28 3-2 Molecular Orbital Theory
two limit cases: The Spatial wavefunction on each of two H atoms forms linear combinations 2019/4/6 复旦大学化学系

29 3-2 Molecular Orbital Theory
The normalized LCAO wavefunctions are orthogonal. 2019/4/6 复旦大学化学系

30 3-2 Molecular Orbital Theory
Discussion The wavefunctions from two H atoms are not orthogonal and the overlap integral is a function of the internuclear distance. K<0 2019/4/6 复旦大学化学系

31 3-2 Molecular Orbital Theory
Anti-bonding Anti-bonding bonding bonding Diagram of H2+ energy levels Potential energy surface for H2+ 2019/4/6 复旦大学化学系

32 3-2 Molecular Orbital Theory
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33 3-2 Molecular Orbital Theory
Electronic structure 2019/4/6 复旦大学化学系

34 3-2 Molecular Orbital Theory
Electronic structure 2019/4/6 复旦大学化学系

35 3-2 Molecular Orbital Theory
Nature of Covalence Bond Redistribution of electron density lowering the system energy makes the molecule stable Interatomic attraction or repulsion is determined by the change of the electron density In a bonding ortital, the nuclei are attracted to the accumulation of electron density in the internuclear region. In an antibonding ortital, the nuclei are attracted to an accumulation of electron density outside the internuclear region vs. 2019/4/6 复旦大学化学系

36 3-2 Molecular Orbital Theory
The Hamiltonian of a Molecule Molecular Orbital R.S.Mulliken 2019/4/6 复旦大学化学系

37 3-2 Molecular Orbital Theory
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38 3-2 Molecular Orbital Theory
Building Principle in Molecular Orbital --- by Hund Hund Linear Combination of Atomic Orbitals to Molecular Orbital What is the reason? G.Herzberg J.E. Lennard-Jones 2019/4/6 复旦大学化学系

39 3-2 Molecular Orbital Theory
A moulding molecule AB Which kinds of atomic orbitals can be used to construct the molecular orbitals? 2019/4/6 复旦大学化学系

40 3-2 Molecular Orbital Theory
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41 3-2 Molecular Orbital Theory
Only AOs of reasonable similar energies contribute substantially to a given MO. (energy closer) 3 All orbitals of the appropriate symmetry contribute to a molecular orbital (symmetry) 1 The great the overlap, the great the bond strength (principle of maximum overlap) 2 2019/4/6 复旦大学化学系

42 3-2 Molecular Orbital Theory
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43 3-2 Molecular Orbital Theory
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44 3-2 Molecular Orbital Theory
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45 3-2 Molecular Orbital Theory
The symbol of molecular orbital Homonuclear Diatomic Molecules Heteronuclear atomic Molecules 2019/4/6 复旦大学化学系

46 3-3 the structure of diatomic molecules
Eigenenergy of atomic orbital (eV) 2019/4/6 复旦大学化学系

47 3-3 the structure of diatomic molecules
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48 3-3 the structure of diatomic molecules
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49 3-3 the structure of diatomic molecules
2019/4/6 复旦大学化学系

50 3-3 the structure of diatomic molecules
2019/4/6 复旦大学化学系

51 3-3 the structure of diatomic molecules
The energy for a given molecular electronic configuration of a diatomic molecule is dependent upon the angular momentum state of the system in much the same way as in the case for atoms. 2019/4/6 复旦大学化学系

52 3-3 the structure of diatomic molecules
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53 3-3 the structure of diatomic molecules
+ + - 2019/4/6 复旦大学化学系

54 3-3 the structure of diatomic molecules
Filled shell Unfilled shell The value of angular momentum is characterized by the molecular orbital occupied by the unpaired electron.. 2019/4/6 复旦大学化学系

55 3-3 the structure of diatomic molecules
The ground-state configuration of oxygen molecule is 2019/4/6 复旦大学化学系

56 3-3 the structure of diatomic molecules
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57 3-3 the structure of diatomic molecules
Select rule of electronic state 2019/4/6 复旦大学化学系

58 3-3 the structure of diatomic molecules
Comparison of VB & MO 2019/4/6 复旦大学化学系

59 3-3 the structure of diatomic molecules
Comparison of VB & MO 2019/4/6 复旦大学化学系

60 Linus Pauling 1901–1994 American chemist
One of the few recipients of two Nobel prizes. His paper “The Nature of the Chemical Bond and the Structure of Molecules and Crystals” won him the 1954 Nobel Prize in chemistry. Won the peace prize in 1962. 2019/4/6 复旦大学化学系

61 Orbital Hybridization
In 1931, Linus Pauling showed that wave-functions from s orbitals and p orbitals could be combined to form hybrid atomic orbitals. Some properties of hybrid orbitals 2019/4/6 复旦大学化学系

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64 Summary of Hybrid Orbitals & Their Geometries
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65 y sp3 Hybridization: x 2019/4/6 复旦大学化学系

66 2019/4/6 复旦大学化学系

67 y x 2019/4/6 复旦大学化学系

68 2019/4/6 复旦大学化学系

69 N H 3 1 2 2019/4/6 复旦大学化学系

70 2019/4/6 复旦大学化学系