Transcript How to build an atom

Charles Hakes
Fort Lewis College
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Chapter 2
Spectroscopy /
Review
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Fort Lewis College
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Outline
• Test Wednesday
• Spectroscopy
• Check posted grades!
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Fort Lewis College
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Misc
• If you received a C- or below (or any
grade you have questions about) for
your mid-term grade, please come by
my office to discuss your situation.
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Fort Lewis College
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Test Topics
• Chapter 0 - review
• Chapter 1 - review, and add
• 1.3 Kepler
• 1.4 Newton
• Chapter 2 - review, and add
• 2.4 Blackbody radiation
• 2.5 Spectroscopy
• Chapter 4 - The Solar System
• 4.1 inventory (review general properties)
• 4.2 debris (asteroids, meteoroids, comets)
• 4.3 solar system formation (nebular theory)
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Test Topics
• Chapter 5 - Earth and Moon
• Entire chapter (particularly atmospheres)
• Chapter 6 - Terrestrial Planets
• 6.3 and 6.8 atmospheres (supplement to 5.3)
• Other sections - just a quick read, on your own.
• Chapter 7 - just a quick read, on your own.
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Fort Lewis College
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Spectroscopy
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ROY G BIV
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Fort Lewis College
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ROY G BIV
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red
orange
yellow
green
blue
indigo
violet
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Figure 2.11
Spectroscope
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Figure 2.12
Emission Spectrum
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Figure 2.15
Absorption Spectrum
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Figure 2.16
Kirchhoff’s Laws
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Figure 2.13
Elemental Emission
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Figure 2.14
Solar Spectrum
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But where do those lines come from?
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Fort Lewis College
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Background
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At the end of the 19th century, many scientists believed
that they had “discovered it all” and that only details
remained to be filled in. (Like why are those spectral lines
there.)
Electromagnetic energy appears to come in “packets”,
called photons.
Particle nature of photons helps explain interactions with
matter.
Photon energy is directly proportional to frequency.
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Fort Lewis College
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Quantum Mechanics
(How to build an atom)
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Fort Lewis College
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How to Build an Atom
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Components
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Proton - heavy, positive charge
Neutron - heavy, no charge
Electron - light, negative charge
Number of protons defines element type
(atomic number)
Sum of protons and neutrons defines
atomic weight
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Fort Lewis College
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How to Build an Atom
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Almost all atom mass is in the nucleus (protons
and neutrons)
Protons are held together by nuclear force.
(Very strong, but very short range.)
Protons (positive charge) make an
“electromagnetic potential well.” (Attracts
negative charges.)
Electrons (negative charge) are attracted to the
well and “fill it up” until you end up with a neutral
atom.
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Fort Lewis College
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Figure 2.18
Modern Atom - note electron “cloud”
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Some Rules for Atoms
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No two electrons can be in the same state of the
same atom at the same time.
Only certain energy levels are allowed.
Only photons with the same energy as the
difference between allowed atomic states can be
absorbed or emitted from an atom.
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Fort Lewis College
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Hydrogen Spectrum
• Transitions from excited state to
ground state will emit ultraviolet
light.
• Transitions from higher excited
state to first excited state emit
visible photons.
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Fort Lewis College
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Figure 2.19
Atomic Excitation
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Figure 2.20
Helium and Carbon
• Allowed energy levels are
much more complex when
multiple electrons are
involved.
• Allowed energy levels are
much more complex when
multiple nuclei are involved
(molecules).
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Fort Lewis College
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Figure 2.21
Hydrogen Spectra - molecular and atomic
Atomic spectrum shows the Balmer lines
(the “H” lines) - Ha, Hb, Hg, etc.
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Fort Lewis College
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Review Questions?
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Fort Lewis College
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Three Minute Paper
• Write 1-3 sentences.
• What was the most important thing
you learned today?
• What questions do you still have
about today’s topics?
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Fort Lewis College
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