wu5c13 by adel khamis

8/14/2019 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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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



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., 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



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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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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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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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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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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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It has high penetrating power:

..

.


wu5c13 by adel khamis

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