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Chapter 5
Electrons in Atoms
I. The Dual Nature of Matter
A.
Matter and energy
are related
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E=mc
B. As matter gets
smaller it behaves
more like energy
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"As far as the laws of mathematics
refer to reality, they are not certain; as
far as they are certain, they do not
refer to reality."--Albert Einstein
C. Scientists in the early 1900’s observed that
elements emitted unique frequencies of visible
light when heated with a flame
D. Electromagnetic radiation – form of
energy that exhibits wavelike behavior
Visible light is a type of electromagnetic
radiation
To understand how small amounts of
matter ( like electrons) behave we must
study wave properties
II. The Wave Nature of Light
The Electromagnetic Spectrum
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II. Wave Nature of Light
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The wavelength, the frequency, and the
speed of light obey the following
relationship:
wavelength * frequency = speed of light.
The speed of light is usually represented
by c, the wavelength by the lower case
Greek letter lambda, l and the frequency
by lower case Greek letter nu n. In these
symbols, the above formula is:
ln=c
Max Plank
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In his research on the
radiation from a hot
(black) body, Max.
Plank made a simple
proposal.
He suggested that
light consists of
photons.
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The energy, E, of each individual photon
of a monochromatic light wave, is
proportional to the frequency, n, of the
light:
E=hn
where h (= 6.626*10-34 J s) is now
known as the Planck constant. Often, we
write h = 6.626e-34 J s for simplicity.
deBroglie Proposal
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Appealing to symmetry of nature,
deBroglie proposed that electrons, too,
have a wave nature and a wavelength!
In particular, deBroglie proposed that the
wavelength of a body could be found from
Flame Test Lab Questions
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Put the unknowns in order from high to
low energy.
Explain why the order makes sense
according to what you know about
wavelength.
Why do the different elements in the lab
emit different frequencies of light.
Electron Configuration Notation
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Aufbau principle – electrons occupy the
lowest energy orbital possible
Pauli exclusion principle – if two electrons
occupy the same orbital they must have
opposite spins (no two electrons can have
the exact 4 same quantum numbers)
Hundz rule – electrons occupy orbital
within a sub-shell singly until they have to
pair