wu5c13 by Adel Khamis
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Transcript of wu5c13 by Adel Khamis
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Unit Five -101- Chapter Thirteen
Rutherfords Model for atom:
The atom consists of a . in which most
of .. of the atom is centered.
The atom dynamic, where the electrons
...
The atom is electrically .., where
Most of the size of the atom is ,
which means that
..
Challenges to Rutherfords model:
I) Stability of the atom:
This explanation is undermined Maxwell Hertzs theory.
Maxwell Hertzs theory:
Conclusion:
According to Rutherfords model, the electron ..
path, which means that the electron moves with
.
According to Maxwell Hertzs theory, the electron must
.
Work Sheet 2007/2008
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Unit Five -102- Chapter Thirteen
II) Atomic spectra for elements:
Since the electrons rotate the
nucleus, then the atom must
emits electromagnetic waves
with . wavelength
(.. spectra).
The experimental observation
found that the electromagnetic
radiation is in form of discrete
nature (. spectra)
occurring wavelength
characteristics the element.
Question:
Compare between Thomson model and Rutherford
model of atom.
Bohrs Model for atom:
Bohrs model depends on the Rutherfords findings in
three items:
At the center of the atom there is ...
.
.. charged electrons move around
the nucleus in shells, each shell has
Work Sheet 2007/2008
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Unit Five -103- Chapter Thirteen
., and the electron (does/ does not) emit radiation as long as it remain
in its shell.
The atom is electrically , since ...
..
Then Bohr adds another three items:
If an electron moves from outer shell of energy E2 to inner shell of energy
E1, it the difference of energy E2 -E1 in form of ..
of energy ...
The .. force (Coulombs force) and the .. force
(Newtons force) are at (work / dont work) in the atom.
The radius of the shell can be estimated by considering that the wave
accompanying to the electron form number of standing
wave.
Example:
The length of the energy level is
..
It contains integer number of
wavelength which equal to
.. ()
Then .. = .
Emission of light from Bohrs atom:
When Hydrogen atom stimulated
by .. energy, its
electron moves to .
energy level, and the excitation
Work Sheet 2007/2008
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Unit Five -104- Chapter Thirteen
differ from atom to another, where the electron may move to any higher
energy level (n=2, n=3 or n=7)
Electron remains at the exited level for .. time lifetime (nearly
.. sec) then it moves to ... level.
When the electron return to the lower level it (gain / emit) photon of
energy .. =E2 E1.
The liner spectrum of hydrogen consists of five series.
Liner spectrum of hydrogen gas:
Leymans series:
The electron moves from any higher
energy level to the level .. (n=..).
This series lies in . range.
Balmers series:
The electron moves from any higher
energy level to the level .. (n=..).
This series lies in . range.
Paschens series:
The electron moves from any higher energy
level to the level .. (n=..).
This series lies in . wavelength
of trange.
Brackets series:
The electron moves from any higher energy
level to the level .. (n=..).
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Unit Five -105- Chapter Thirteen
This series lies in . wavelength of trange.
Pfunds series:
The electron moves from any higher energy level to the level ..
(n=..).
This series lies in . wavelength of trange.
Spectrometer:
It is an apparatus used to
.
Structure:
Source of rays: a light source in front of . at . of a
lens, the width of the slit
.
Analytical device: . placed
on ..
Telescope: telescope consists of
Mechanism:
To obtain pure spectrum, the slit is
bright by light to fall in
the prism with angle adjusted to
The prism analysis the light into .., producing parallel
beam for each color, which are (parallel / not parallel) to the other colors.
The objective focal plane,
and by using the pure spectrum can be observed.
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Unit Five -106- Chapter Thirteen
Spectra:
Spectra can be classified according to its nature into continuous and line
spectrum.
Continuous spectrum:
..
Line spectrum:
..
Also, spectra can be classified according to its source into absorption and
emission spectrum.
Emission spectrum:
..
Absorption spectrum:
.,
which are the (same / not same) wavelength emit by the emission
spectrum for the same element.
Fraunhofer lines:
It is (emission / absorption) spectrum of the elements in the sun, which
help to detect that sun consists of .. and ..
X-ray:
It is . waves, between
rays and . rays.
It has (high / low) frequency, (high / low) energy
and (long / short) wavelength (10-13 10-8 m).
It had been discovered by Rontgen.
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Unit Five -107- Chapter Thirteen
Properties of X-ray:
..
..
..
..
Coolidge tube:
It is used to produce X-ray.
Electrons emit from ...
Electrons gain large amount of energy due to .
When the electrons , its energy produce x-ray.
Spectrum of X-ray:
It consists of:
Continuous spectrum: Consists of . within certain
range, target material.
Line spectrum: corresponding to
. characteristic of the
target material; called
..
Continuous radiation:
The velocity of the colliding electrons
decrease due to ..
..
According to Maxwell Hertz theory, the decrease of electrons velocity
leads to .....................
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Unit Five -108- Chapter Thirteen
Since the electron loses its velocity gradually, therefore
.. producing . radiation.
This radiation is called the . radiation, bremsstrahlung or
.. radiation.
Characteristic radiation:
It required (high / low) potential difference, and it may not produce at
low potential difference between the .. and .
Under high potential difference the electron impact with the (inner /
outer) electron of the atom, casing to release or to move to higher energy
level.
An electron form higher level replaces the releasing electron (or the
exited one) and the of its energy produces the ..
radiation.
It does not depend on the ., but it depend on the
, where the increase of its atomic number leads to
. the frequency of radiation, and .. the wavelength.
Its frequency and wavelength can be calculated from the relation:
E=.
..........
..........E =
Important applications of x-ray:
It diffract by passing through the
material atoms, which act as diffraction
grating, casing the x-ray to form bright
and dark fringes, similar to double slit experiment:
Therefore It used ..
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Unit Five -109- Chapter Thirteen
It has high penetrating power:
..
.
Work Sheet 2007/2008