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Spin and Atomic Physics 1. 2. 3. Review on quantum numbers Quiz 11.11 Topics in this chapter: Today The spin and the Stern-Gerlach experiment. Fermion, Boson and the Pauli exclusion principle. Multi-electron atoms and the Periodic Table. Characteristic X-rays. The building blocks for our Universe Intrinsic property that defines a fundamental particle: Mass Charge Spin The quantum numbers that defines the electron energy state in an atom: Principle: n 1, 2,3,... Orbital: l 0,1, 2,3,...,n 1 L l l 1 Magnetic: ml 0, 1, 2, 3,..., l Lz ml Spin: ms s, s 1,...,s 1,s S s s 1 S z ms Fermions and Bosons Spin is an intrinsic property of a particle like mass and charge. Fermions (half-integral spin) Particle Electron, eProton, p Neutron, n Neutrino, ν Omega, Ω- s Bosons (integral spin) Particle s ½ ½ ½ ½ ½ Pion, π 0 Alpha Photon, γ Deuteron, d Graviton 0 0 1 1 2 Multi-electron atoms Inner electrons screen outer electrons. Small-l states approach closer to the nucleus than do large-l states. Large-l states contribute to electron energy. The energy ordering is affected: Energy Filling the electrons H: 1s1 He: 1s 2 Li: 1s 2 2s1 Be: 1s 2 2s 2 Z Multi-electron atoms Electrons fill energy states from low to high: This is the physics basis for the Periodical Table. H: 1s1 He: 1s 2 B: 1s 2 2s 2 2 p1 Li: 1s 2 2s1 Be: 1s 2 2s 2 Ne: 1s 2 2s 2 2 p 6 The Periodic Table of the Elements The characteristic X-rays Energy needed to ionize the atoms Review questions Why the energy state ordering of an electron in an atom is affected by large orbital quantum numbers? The state of an electron in an atom is completely defined by its quantum numbers. The energy of the electron is also a function of Z, the total positive charge of the nucleus. For the electrons with the same quantum numbers, what is the trend of their energy with respect to Z ? Preview for the next class (11/11) Text to be read: 10.7 and 10.8 Questions: What is the mechanism for a diode to be conductive only in one direction? Generally speaking, there are two types of transistors, the bipolar and the field effect. Find out the physics basis for their function. If vacuum tube is to be compared to the transistors, which type is closer? Homework 13, due by 11/18 Problems 8.49 on page 342.