when heated to high temps, gases give off light. if this light is passed through a slit, then...
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When heated to high temps, gases give off light.If this light is passed through a slit, then through aprism or diffraction grating, the following patterns are seen:
bright-linespectrum
dark-linespectrum
Why are there only separate (discrete) colors or lines?
the lines are images of the slits
Or if a light with a continuous spectrum is passed through a cold gas and then through a prism, you get:
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Models of the atom:
I. _____________________: In 1897, discovered e-’s were
________ mass and ____________________ charged. Since
he also knew that atoms as a whole were ______________,
he developed the ______________________________ model:
negative e-
are the
____________
positive charge is ________________
distributed in a___________________
“raisin/plum pudding”
J.J. Thomson
low negativelyneutral
One _________ :atom
uniformly “pudding”
raisins
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phosphorescentscreen
One of JJ's experimentswith electrons:
battery
Which side of the battery was positive?
electron beam
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_____________________ : In 1909, he fired ___________
particles (positively charged ____________ nuclei) at thin
gold foil:
particle
Au foil
only 1 in 8000 were
scattered ____________
________ were not
scattered or were
scattered through
_____________ anglesHis conclusion:
The ___________________________ mass is concentrated in
_________________________ at the atom's _____________ .
He called this the ________________ of the atom.
Rutherford alphahelium
most
backwards
positively charged
a very small volume
only small
centernucleus
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II. As a result of Rutherford's experiment, the
___________________ model was developed:
The e-'s ___________ the nucleus similar to how
________________ orbit __________________ .
______________charge
concentrated in the
_____________
size of nucleus ~ ___________________ of
` the diameter of atom
positive
orbit
1/10,000
solar system
planets the Sun
e-
e-
nucleus
One atom:
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_____________________with the solar system model: 1. Circular orbital motion q _________________
2. Accelerating q ______________emitted from atom
3. Energy radiated orbits will _____________________
4. All atoms should ___________________in a short time
5. As they collapse, the e- should______________________
and the atom should _____________________emit a higher
and higher ______________________ of light
6. This should produce a ____________________spectrum.
but _______________ spectra were observed.
accelerates
radiation
get smaller
collapse
revolve faster
Problems
continuouslyfrequency
continuousdiscrete
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But only saw:
Why?
Should see:
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III. The Bohr model for ___________________: 1. The 1 e- in H____________________ or ______________________the nucleus. It __________ in a ___________.2. The e- can only be found at ______________ (certain specially allowed) distances, which are unfortunately still called __________________ . Each orbital has a _____________ number,____ . a/ The orbital _____________to the nucleus is called the ____________________and has n = ____. It has the ______________ energy = ______________.
b/ The orbital furthest from the nucleus has the ______________energy and has n =_____. The energy
of that orbital = ____. In that case, the e- is said to be _______________ , which means it is ________________ from the atom completely.
hydrogen, H
does not orbitaround
discrete
move
“orbitals.”
nquantum
ground state
exists "state"
closest
1lowest -13.6 eV
highest ∞
ionized.
0removed
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n=1
n=2
n= ∞
etc…
e- is___________
_________state ofelectron
n=3
The ______ e- can be foundat ______ level
A. Bohr model of H atom:
n= 2 to ∞ are called____________ states
proton
----- = _____________orbitals
ground
ionized
“excited”one
any
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If an e- moves from to a ___________ energy orbital to a __________one, a photon of light is ___________ (given off).
The ____________ of the emitted photon: Eph =
n=1
n=2
n=3
photon_________
B. Photon _________________ :emission
lowerhigher
emitted
Ei - Efenergy
emitted
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Ei =
Ef =
Eph =
Easy way: IGNORENEG. SIGNS AND JUSTSUBTRACT!!!
Eph =
=
Eph = Ei – Ef
E3=
E2 =
E3 – E2
3.40 – 1.51
1.89 eV
Reference Tables: page 3, top left.
-1.51 eV
-3.40 eV
=
– 1.51 – (-3.40)
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The __________ of the absorbed photon: Eph =
photon_________
If an e- moves from a ___________ energy orbital to a __________one, a photon of light is ___________ (taken in).
C. Photon _________________ :absorption
lower
higher absorbed
Ei - Ef
n=1
n=2
n=3
energy
absorbed
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Ef =
Ei =
Eph =
Eph =
=
Eph = Ei – Ef
E3 = -1.51 eV
E1= -13.60 eV
E1 – E3
(ignore neg. signs)
13.60 – 1.51
12.09 eV
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D. Energy ____________________:
atom
Atom __________ energy
as e- moves __________
photon
___________
___________
Emission (the ____________of light):
Absorption (the ____________ of light):
atom
Atom _________energy
as e- moves_________
photon
__________
__________
conservation
birth
death
loses
down
removesenergy
bringsenergy
gains
up
In both cases: _________________ = ___________________energy gained energy lost
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2. No _______________________ jumps are allowed!!!
Only jumps from one ______________energy level or
orbit to another ____________ energy level are
allowed.3. That is why _______________________ energy photons
can be emitted or absorbed by atoms..
4. Since Eph = hf, only certain __________________(colors)
are produced.
5. That is why photon energies
are ___________________(only
certain values are allowed).
1. The technical term for “jumps” is____________________.
E. NOTES:transitions
“inbetween”
allowed
allowed
only certain
frequencies
“quantized”
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Bigger e- jumps more (transitions) more _________
_____________ frequency photons
in ___________________ and beyond
Eph = Ei – Ef = hf
Little e- jumps less _________
(transitions) less _________ _____________ frequency photons
in ____________________ and lower
ΔE= amount of e-____________"jump"
ΔEEph
blue, violet, UV
ΔE
Eph
higher
red, IRlower
This is true for _______________ and _______________ .emission absorption
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high f low f
BIG jumpslittle jumps
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_______ transitions
_______energy light
involv
e
_______ transitions
_______energy light
involv
elittle
low
big
high
Which transitions involve visible light? to the n=2 level
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Where would thesephotonsappear in thespectrum?
Andthese?
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F. ________________ : Jumps from any level to n = ___ will___________the e- from the atom.
Ionization _________________:The _____________required to ___________an e- from an atom.
What is the ionization potential for a H atom thathas an electron in the groundstate?
What is the ionization potential for a H atom thathas an electron in the n=3state?
13.6 - 0= 13.6 eV
1.51 - 0= 1.51 eV
Ionization ∞
remove
potentialenergy
remove
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Notice: Mercurygas also has a fun diagram!
But mercury hasletters instead of numbers.
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G. So where do _________________ (bright line) and _____________________spectra come from?
The missing colorsare the __________ onesthat were_____________by the gas.The heated gas
absorbs, then emitsonly those photonsfrom _____________energy transitions.
absorptionemission
Unless the source is a low-density gas, interactions with otheratoms blur the lines into a _________________spectrum.
allowed
continuous
absorbed
same
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The same transitions produce same lines:
photon absorbed
photon emitted
same transition
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•Each element has a _____________electron structure.•The electrons make _______________transitions.•Each transition produces a spectral ___________.•The set of lines is a __________________for that element.
Ex: Atomic absorption spectroscopy:
white light
gas orliquid
containing______________
elements that absorb
certain photons
slit
_________:disperseslight
___________
spectrum
uniqueunique
line
fingerprint
unknown
prism
absorption
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Sun
The Sun produces a continuous spectrum b/cthe interaction of many gases blurs the energy levels.
Atmosphere of Sun – absorbsonly photons that can “jump” levels of gases in it. That is how helium was discovered.
light after passingthrough atmosphereproduces a dark linespectrum
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Stars broad lines dense gas compact star red shifted star moving away blue shifted star approaching
incr
easi
ng
tem
pera
ture
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V. Bohr’s model could NOT explain why e- could onlyhave ______________orbitals and energies. This was later explained by_________________________:
The e- acts like a __________ and __________________interferes with ___________ as it wraps itself around the ________________:
This can only occur at certain ______________ distances from the nucleus.
Louis DeBroglie
constructively
nucleus
itself
discrete
discrete
nucleus
electron________
wave
orbits
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The electrons form “standing waves” around the nucleus.
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Electrons can act like waves. The wavelength’s of e- depend on their speed, but they are generally very small. That allows us to take pictures of very small things.
fruit fly
colorized house fly
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surface of poison ivy
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VI. The ___________Model:
1. The electron is described by a ________ function, .”
2. The square: 2is the ___________________ of finding
an electron at a certain position. The e- is most likely to
be found where the "probability cloud" is ________________
3. The electron is no longer thought to be located at
a ________________ location, but may be ______________ .
4. The locations of highest probability correspond
to the positions of the old________________________.
Cloud
probability
_________ orbitals:
wave
definite
densest
spread out
Bohr orbits
_________ clouds
Bohr probability
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Mass has a dual nature: particles or waves.
Light has a dual nature: particles or waves.
mass usuallyacts like aparticle
mass sometimesacts like a wave
light usuallyacts like awave
light sometimesacts like aparticle