Transcript Precursors to Modern Physics

Spin and Atomic Physics
1.
2.
3.
Review on quantum numbers
Quiz 11.11
Topics in this chapter:
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Today
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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
Sz  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: 1s2 2s2 2 p1
Li: 1s 2 2s1
Be: 1s 2 2s 2
Ne: 1s2 2s2 2 p6
The Periodic Table of the Elements
The characteristic X-rays
Energy needed to ionize the atoms
Review questions
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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)
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Text to be read:
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10.7 and 10.8
Questions:
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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.