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2. Atoms and Electrons

2. Atoms and Electrons

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2. Atoms and Electrons

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  1. 2. Atoms and Electrons How to describe a new physical phenomenon? New natural phenomenon Explained Experiments confirm new phenomena Previously existing theory Not explained New theory Predicts new phenomena

  2. How to describe a new physical phenomenon? New phenomenon Previous Theory New comprehensive theory

  3. -34 h=6.625*10 Js Planck constant E – Energy of photon f – Frequency of light Shortest Course in Quantum Mechanics Observation: Electrons and atoms did not obey the classical laws of mechanics. New theory: Quantum mechanics predicts the way in which electrons behave in solids.. Postulate: The light is quantized. The smallest discrete unit of energy is photon. E=h·f

  4. Shortest Course in Quantum Mechanics, Cont. Nobel Prizes: 1918 Planck for thediscovery of energy quanta 1921 Einstein for the law of the photoelectric effect Wave Dual nature: Particle Wave nature: electromagnetic wave f=1/ T (Hz) =c/f (m) wavelength Light: Particle nature : photon p=h/ momentum of a photon

  5. Shortest Course in Quantum Mechanics, Cont. Atomic spectra: Bohr model of atom Nobel prize 1922 Niels Bohr for structure of atoms and radiation emanating from them • Bohr postulates: • Electron exists in certain stable circular orbits about the nucleus and does not give off radiation • Electron may shift to an orbit of higher or lower energy by absorbing or emitting a photon of energy hf • Angular momentum is quantized p =m v r = n h/2 

  6. Shortest Course in Quantum Mechanics, Cont. Atomic spectra: Bohr model of atom E 3 e- E 2 hf = E3-E1 Emission 31 E 1 e- hf =E2-E1 Absorption 12

  7. Shortest Course in Quantum Mechanics, Cont. Heisenberg Uncertainty Principle (Nobel prize 1932 for the creation of quantum mechanics) The more precise you know the position of a particle , the less precise you know the momentum of the particle: x px≥ h/2 The more precise you know the time, the less precise you know the energy: E t ≥ h/2

  8. Shortest Course in Quantum Mechanics, Cont. Schrodinger Wave Equation Dual nature of Electron : • Wave: • Wave function (x) • Schrodinger Wave Equation • (x) *(x) dx is probability that the position of electron is within (x, x+x) • Particle: • Mass • Position • Momentum • Energy

  9. Shortest Course in Quantum Mechanics, Cont. Schrodinger equation and solution for the potential well problem will be presented in class.