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Atomic Struture Questions Question 1
| a) |
Give a brief description of Rutherford’s alpha particle scattering experiment. |
| b) |
State the main conclusions of the experiment. |
| c) |
An a particle of mass 6·68×10-27kg, is moving straight towards a gold nucleus (Z = 79) at a speed of 0·01c (0·01 times the speed of light). Calculate the minimum distance between the two particles (the distance of closest approach). |
Question 2
| a) |
Bohr developed a model of the hydrogen atom. |
|
i) |
What particles enter into this model? |
|
ii) |
Describe the motion he assumed for each of the particles. |
|
iii) |
What forms of energy did he include when calculating the total energy of the atom? |
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iv) |
What does it mean to describe a physical quantity as being "quantized"? |
|
v) |
Which quantity did Bohr consider to be quantized when developing his model? |
| b) |
Use Bohr’s theory to explain why hydrogen emits a line spectrum rather than a continuous spectrum. |
Question 3
|
In a simplified
version of
Millikan’s oil drop
experiment, a drop
of radius r = 1·75×10-3mm,
is between two
parallel metal
plates separated by
distance d =
9mm. |
 |
|
When the voltage
across the plates is
V =
2kV, the drop
remains stationary.
The density of the
oil is
r
= 800kgm-3.
Use this information
to estimate the
number of singly
ionised atoms in the
drop. |
Question 4
|
The diagram below
represents the
energy levels in a
hydrogen atom. |
|
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| a) |
Convert the energies
into Joules. |
| b) |
Calculate the
wavelength of the
radiation given out
by each of the three
transitions shown on
the diagram. In each
case state whether
the quantum of
radiation is in the
u.v., the visible or
the i.r. part of the
spectrum. |
|
c) |
Calculate the
wavelength of the
radiation needed to
ionise a hydrogen
atom which is in its
ground state. Answer
in Joules. |
|
d) |
Calculate the energy
of an electron in
level n = 5. Answer
in electron-volts. |
Question 5
| a) |
Discuss briefly
deBroglie’s
hypothesis and
mention one
experiment which
gives evidence to
support it. |
|
b) |
Calculate the
wavelength of the
“deBroglie wave”
associated with an
electron in the
lowest energy Bohr
orbit. (The radius
of the lowest energy
orbit according to
the Bohr theory is
5·3×10-11m.) |
Question
6
| a) |
Draw a labelled diagram of an
X-ray tube. |
| b) |
Explain the characteristic (or line) part of an
X-ray spectrum. |
|
c) |
Derive
a formula to calculate the minimum wavelength of
X-rays in the continuous part of an X-ray
spectrum.
Use your formula to calculate the highest
frequency of X-rays given by a tube which uses a
high voltage supply of 25kV. |
Question
7
|
Calculate the wavelengths of the “deBroglie”
waves associated with |
| a) |
a
1kg
mass moving at 50ms-1 |
|
b) |
an
electron which has been accelerated by a p.d. of
500V. |
Question
8
|
How
much energy could (in principle) be obtained from
1u of
mass?
(Answer first in J then in MeV.) |
Question
9
|
A
proton has a mass of 1·0078u and a neutron has a mass of 1·0078u. A helium nucleus has a mass of 4·0026u. Calculate the energy given out when a helium nucleus is
formed. Answer in MeV. |
Question
10
|
The
fission of a uranium 235 nucleus into barium and
krypton produces about 200MeV of energy. Find the
mass loss during this reaction. (Answer first in
kg then in u.) |
Question
11
The
neutron was discovered when beryllium
 was
bombarded with
a
particles. Copy and complete the following
equation which describes the reaction. |
|
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Question
12
|
A uranium 235 nucleus can
decay into a thorium (Th) nucleus by the emission
of an
particle. Write an equation which describes this
decay. |
Question
13
|
Copy
and complete the following equation which
describes a possible nuclear fission process. |
|
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Question
14
A
neptunium nucleus (Np 239) can decay into a
plutonium nucleus (Pu 239) and a
particle. Write an equation to describe this
reaction. |
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© David Hoult 2009 |
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