ATOMIC PHYSICS

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ATOMIC PHYSICS
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History of Atomic Structure

• Thompson Model
• Plum Pudding Model
• Rutherford Model
• Nucleus
• 99 mass of atom
• Electrons surrounding nucleus
• Take up most of space, negligible mass
• Bohr Model
• Electron orbital model
• Electrons occupy discrete energy levels
• Energy levels quantized
• Modern Model
• Electron cloud (region of high probability to
  find electron

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Ernest Rutherford Bio
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RUTHERFORD EXPERIMENT
SCREEN
Au FOIL
Pb SHIELD
ALPHA SOURCE
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The Rutherford Experiment 1911
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Rutherford ExperimentJ.J. Thompson Model
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Rutherford ExperimentRutherford Model
Au atoms mostly vacant space!
charged nucleus contained most of matter,
occupied very little space.
- charges occupy most of the space, very little
matter
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Balmer (1885)
H atom Emission Spectra
Balmer Equation
R Rydbergs Constant 6.84 x 105 m-1
n whole interger s gt 2
n 3,4,5,6
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Niels Bohr Bio
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Bohr Orbital Model
H atom energy level diagram
(eV)
ionization
0.00
-0.38
-0.54
-0.85
-1.51
-3.4
-13.6
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Bohr Orbital Model
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Bohrs Postulates

• Radiationless energy states exist
• During transition from one E state to another
• Ef Ei E photon hf
• Electron wavelength in stable orbit creates
  standing wave
• nl 2pr
• n 1,2,3,

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e deBroglie l Standing Wave
n 4
4l 2pr4
e is ?
No radiation emitted
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Bohrs Postulates (continued)
3. Electron in orbital is in a standing wave
nl 2pr
n 1,2,3,
l h
l h
p
mv
h
2pr

n
mv

mvr
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Bohrs Postulates (continued)
3. Angular Momentum of electron orbits is
quantized

mvr

Angular Momentum
n 1,2,3,
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Balmer Series
Hydrogen Emission Spectra
H atom energy levels
(eV)
e
e
e
e
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Lyman Series
H atom energy levels
ALL PHOTONS ULTRAVIOLET
(eV)
e
e
e
e
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Paschen Series
H atom energy levels
(eV)
ALL PHOTONS INFARED
e
e
e
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H UltravioletAbsorption Spectra
H atom energy levels
ALL PHOTONS ULTRAVIOLET
(eV)
e
e
DE 13.06 ev
e
DE 12.75 ev
DE 12.09 ev
e
DE 10.2 ev
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H Visible Absorption Spectra
Visible spectrum
H atom energy level diagram
(eV)
e
DE 3.02 ev
e
DE 2.86 ev
DE 2.55 ev
DE 1.89 ev
e
e
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Visible Solar SpectrumShowing Prominent
Absorption Fraunhofer Lines
H
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Bohr Orbital Model
H atom energy level diagram
(eV)
ionization
How did Bohr determine these energy values????
0.00
-0.38
-0.54
-0.85
-1.51
-3.4
-13.6
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H atom
r 5.3 x 10-11 m
potential created by proton at r
e
Fe
p
V kq
27.2 V
r
TOTAL ENERGY OF ATOM
ETOTAL PEe KE
PEe qV (-1.6 x 10 19) ( 27.2 V)
PEe - 4.35 x 10 18 J
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H atom (continued)
KE ½ mv2
V ?
Fe kq1q2
Fc mv2
Fe Fc
r
r2
Fe 8.22 x 10-8 N
V 2.18 x106 m/s 5 MILLION MPH
KE ½ mv2 2.2 x10-18 J
-2.2 x 10-18 J
ETOT PEe KE
ETOT -13.6 eV
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H atom (cont.)
Fc Fe
kq2
mv2
r
r2
ETOTAL KE PEe
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Bohr H atom
EARLIER
EARLIER
nh

mvr
mv2
kq2
2p
r
( )
nh
nh
2

v
kq2
m
2pmr
2pmr
r
r a n2
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H Energy Levels
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Balmer Equation Derivation
Ep DE Ef - Ei
Ef - Ei

-
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For Balmer Series
BALMER EQUATION
n 3,4,5,6
BOHRS EQUATION
nf 2
6.84 x 105 m-1
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Balmer Equation Unit Check
1
(kg)
(Nm2/C2)2
(C4)

m
(m/s)
(J s)3
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Hg Energy Levels
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H Energy Level Diagram
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SPONTANEOUS ABSORPTION
Ef
Ei
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SPONTANEOUS EMISSION
Ei
Ef
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STIMULATED EMISSION
Ei
COHERENT PHOTONS IN PHASE, SAME f
Ef
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L. A. S. E. R.
by
of
ight
adiation
mplification
timulated
mmission
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L.A.S.E.R.
Energy pump
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LASER STIMULATED EMISSION
E3
E2
METASTABLE STATE
E1
POPULATION INVERSION
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ATOMIC PHYSICS

• SAMPLE AP QUESTIONS

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AP PHYSICS HOMEWORK 25

NAME _____________________________________ MO
DERN PHYSICS

DATE _________________ PERIOD
___________
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AP PHYSICS HOMEWORK 25

NAME _____________________________________ MO
DERN PHYSICS

DATE _________________ PERIOD
___________
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AP PHYSICS HOMEWORK 25

NAME _____________________________________ MO
DERN PHYSICS

DATE _________________ PERIOD
___________
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AP PHYSICS HOMEWORK 25

NAME _____________________________________ MO
DERN PHYSICS

DATE _________________ PERIOD
___________
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AP PHYSICS HOMEWORK 25

NAME _____________________________________ MO
DERN PHYSICS

DATE _________________ PERIOD
___________
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Sample Prolem 2