Quantum Chemistry: Our Agenda Birth of quantum mechanics (Ch. 1) Postulates in quantum mechanics (Ch. 3) Schrödinger equation (Ch. 2) Simple examples of V(r) Particle in a box (Ch. 4-5) Harmonic oscillator (vibration) (Ch. 7-8) Particle on a ring or a sphere (rotation) (Ch. 7-8) Hydrogen atom (one-electron atom) (Ch. 9) Extension to chemical systems Many-electron atoms (Ch ) Diatomic molecules (Ch. 12) Polyatomic molecules (Ch. 13) Computational chemistry (Ch. 15)

“Quantum Mechanical” Questions Why do the electrons in an atom not follow a spiral trajectory to fall into the nucleus? Why does the light emitted by a hydrogen discharge lamp appear at only a small number of wavelengths? Why does graphite conduct electricity and why does diamond not? Why is the bond angle in H 2 O different from that in H 2 S? Why Quantum Mechanics? “We need to be able to think in terms of quantum mechanical models because: (1)Technology is increasingly based on quantum mechanics; (2)More scientists become increasingly focus on nm-scale atomic/molecular level. What is an example of the “quantum mechanical” technology (or phenomena)? Why is it “quantum mechanical”?

Lecture 1.5 Birth of Quantum Mechanics. Historical Background. Experiments and Theories Engel, Ch. 1 Quantum chemistry, D. A. McQuarrie (1983), Ch. 1 Molecular quantum mechanics, Atkins & Friedman (4 th ed. 2005), Ch. 0 Introductory quantum mechanics, R. L. Liboff (4 th ed, 2004), Ch. 2 Experiments are the only means of knowledge at our disposal. The rest is poetry, imagination. - Max Planck -

1885 – Johann Balmer – Line spectrum of hydrogen atoms 1886 – Heinrich Hertz – Photoelectric effect experiment 1897 – J. J. Thomson – Discovery of electrons from cathode rays experiment 1900 – Max Planck – Quantum theory of blackbody radiation 1905 – Albert Einstein– Quantum theory of photoelectric effect 1910 – Ernest Rutherford – Scattering experiment with  -particles 1913 – Niels Bohr – Quantum theory of hydrogen spectra 1923 – Arthur Compton – Scattering experiment of photons off electrons 1924 – Wolfgang Pauli – Exclusion principle – Ch – Louis de Broglie – Matter waves 1925 – Davisson and Germer – Diffraction experiment on wave properties of electrons 1926 – Erwin Schrodinger – Wave equation – Ch – Werner Heisenberg – Uncertainty principle – Ch – Max Born – Interpretation of wave function – Ch. 3 History of Quantum Mechanics particle wave

1900 – Max Planck  Quantum theory of blackbody radiation

1886 – Heinrich Hertz – Photoelectric effect experiment 1897 – J. J. Thomson – Discovery of electrons 1905 – Albert Einstein– Quantum theory of photoelectric effect 1923 – A. H. Compton – Scattering experiment of photons off electrons

1885 – Johann Balmer – Line spectrum of hydrogen atoms 1910 – Ernest Rutherford –  -particle scattering experiment 1913 – Niels Bohr – Theory of atomic spectra

1924 – Louis de Broglie – Matter waves 1925 – Davisson & Germer – Electron diffraction 1926 – G. P. Thomson – Electron diffraction

J. J. Thomson, dad, was awarded the Nobel prize (1906) for showing that the electron is a particle; G.P. Thomson, son, was awarded the Nobel prize (1937) for showing that the electron is a wave. Statistical, i.e., only after a large amount of observations (or particles)