Atomic and Nuclear Flashcards
(129 cards)
1
Q
Who and when was the plum pudding model of the atom proposed?
A
JJ Thompson in 1904
2
Q
What did JJ Thompson believe atoms were?
A
- Spheres of positive charge.
- With negative charges spread throughout it.
3
Q
Who discovered the current ideas about the structure of the atom?
A
Ernest Rutherford
4
Q
How did Ernest Rutherford discover the current ideas about the structure of the atom?
A
Fired alpha particles at very thin sheet of gold foil.
5
Q
Had the plum pudding model been true, what would Rutherford have expected to observe happening to the alpha particles when he carried out his experiment?
A
- Little to no deflection
- Very small loss in kinetic energy.
- No loss in intensity.
6
Q
What are the properties of an alpha particle?
A
Positive charge
Small volume
Large mass
Very high density
7
Q
What are the properties of a ‘plum pudding’ atom?
A
Atom charge and mass spread over large area.
Low density of mass and charge.
8
Q
What didi Rutherford actually observe happing to the alpha particles in his experiment?
A
Drop in intensity.
No drop in kinetic energy.
Particles spread all over vacuum chamber through to 180 degrees.
9
Q
How did Rutherford find out where all the alpha particles were going in his experiment?
A
Out detector on moveable tracks.
10
Q
How were the alpha particles spread in Rutherford’s experiment?
A
Few had deflections greater the 90 degrees.
Some had large deflections.
Most were unaffected or had slight deflections with no loss in kinetic energy.
Very small number had deflections of 180 degrees.
11
Q
What is the name of Rutherford’s model of the atom?
A
Nuclear model.
12
Q
How did Rutherford explain the high number of non deflected particles that retained all or most of their kinetic energy in his experiment?
A
Atom must contain mostly empty space.
13
Q
How did Rutherford explain the particles that were deflected and their relatively low numbers compared to those reflected in his experiment?
A
Must be region of atom very small but contained all of positive charge.
14
Q
How didi Rutherford explain the neutral charge of the atoms in his experiment?
A
All electrons must be in orbit around nucleus.
15
Q
What is the mass of the proton?
A
1
16
Q
What is the mass of the neutron?
A
1
17
Q
What is the mass of the electron?
A
1/1840th
18
Q
What is the charge of the proton?
A
+1
19
Q
What is the charge of the neutron?
A
None / 0
20
Q
What is the charge of the electron?
A
-1
21
Q
What is the mass number of an atom?
A
Number of protons plus number of neutrons in neutral atom.
22
Q
What is the atomic number of an atom?
A
Number of protons (same number as number of electrons) in neutral atom.
23
Q
Why do some atoms have nucleus which is unstable?
A
Repulsive forces
Attractive forces
24
Q
What are repulsive forces in an atom?
A
Electrostatic repulsion of close protons.
25
What are attractive forces in an atom?
Strong nuclear force.
26
What happens in an atom when the repulsion of protons becomes larger than the attractive forces?
Nucleus emits radioactive radiation to become more stable nucleus.
27
What are radioactive isotopes called?
Radioisotopes or radionuclides
28
What are some isotopes radioactive?
Nuclei are unstable as have too many or too few neutrons.
29
How can will tell which isotopes will be radioactive?
Look at number of protons compared to number of neutrons of an isotope.
30
How can we see the number of protons in comparison to the number of neutrons of an isotope?
Use graph
31
How must an isotope be stable on a graph?
Use lie on stability line.
32
What happens if an isotope is above or believe the stability line on a graph?
Will give off radiation to get closer to it, and hence become more stable.
33
What are the 3 types of radiation?
Alpha particle
Beta particle
Gamma radiation
34
What does an alpha particle consist of?
2 protons and 2 neutrons.
Same as helium nucleus.
35
What happens when an atom’s nucleus decays?
Releases a alpha particle so loses 2 protons and 2 neutrons.
36
How much does the mass number decrease by when an atom’s nucleus decays?
By 4
37
How much does the atomic number decrease by when an atom’s nucleus decays?
By 2.
38
What is formed when an atom’s nucleus decays?
New element as has different number of protons and neutrons.
39
What does a beta particle consist of?
High energy electron which is emitted by nucleus of decaying atom.
40
What happens when an atom’s nucleus decays and releases a beta particle?
A neutron turns into a proton which stays in nucleus and high energy electron is emitted.
41
How much does the mass number decrease by when a decaying atom emits a beta particle?
Remains the same.
42
How much does the atomic number decrease by when a decaying atom emits a beta particle?
Increases by 1.
43
What is formed when a decaying atom emits a beta particle?
Gained proton so forms new element.
44
What is the conservation of charge?
Charge before = charge after
45
What is gamma radiation?
Form of electromagnetic radiation.
Not type of particle.
46
What happens when an atom’s nucleus decays and emits gamma radiation?
Releases energy in form of electromagnetic radiation.
47
Is a new element formed when when a decaying atom emits gamma radiation?
No as no change in makeup of nucleus.
48
What happens when an atom has sufficient energy or radiation directed upon it?
Electrons may be given sufficient energy (ionisation energy) to free electrons.
49
What is formed when when an atom is given sufficient energy to free electrons?
Positively charged ion as has lost an electron.
50
What is ionisation?
Process by which atom or molecule acquires negative or positive charge by gaining or losing electrons to form ions.
51
What is an isotope?
Variants of same element with same number of protons but varying number of neutrons.
52
Where is radiation found?
All around us.
53
How can the effects of radiation be seen and detected?
Using Geiger-Müller tube.
54
What is a Geiger-Müller tube?
Device that can detect and measure radiation.
55
How is radioactivity detected?
By presence of photographic film which darkens when struck by radiation?
56
What is the electric charge of alpha radiation?
+2
57
What is the relative atomic mass of alpha radiation?
4
58
What is the penetrating power of alpha radiation?
Stopped by paper or few centimetres of air
59
Why is alpha radiation stopped by paper or a few centimetres of air?
Large size.
60
What is the ionising effect of alpha radiation?
Strongly ionising.
61
What is the effect of a magnetic / electric field on alpha radiation?
Weakly deflected.
62
What is the electric charge of beta radiation?
-1
63
What is the relative atomic mass of beta radiation?
1 / 1840
64
What is the penetrating power of beta radiation?
Stopped by few millimetres of aluminium or several metres or air.
65
What is the ionising effect of beta radiation?
Weakly ionising
66
What is the effect of a magnetic / electric field on beta radiation?
Strongly deflected.
67
What is the electric charge of gamma radiation?
0
68
What is the relative atomic mass of gamma radiation?
0
69
What is the penetrating power of gamma radiation?
Stopped by several centimetres of lead or several metres of concrete.
70
What is the ionising effect of gamma radiation?
Very weakly ionising.
71
What is the effect of a magnetic / electric field on gamma radiation?
Not deflected.
72
What is the symbol for alpha radiation?
Infinity symbol but right side missing.
73
What is the symbol for beta radiation?
β
74
What is the symbol for gamma radiation?
γ
75
What is the speed of an alpha particle?
6% c
76
How many collisions does an alpha particle have with air per cm?
100,000 collision / cm
77
What is the speed of a beta particle?
90% c
78
What is the speed of gamma radiation?
c
79
How is the nuclei in a decaying atom that emits gamma radiation different from before?
More stable
80
What is background radiation?
Radiation that takes place naturally and cause by radioactive material in rocks, air, our bodies and partly cosmic rays from outer space.
81
Where is background radiation found?
All around us.
82
What are the main forms of background radiation?
Radon gas - emitted from granite rock.
Potassium- 40 from food absorbed in our body.
Cosmic rays from outer space.
83
What do all the main forms of background radiation have in common?
Dosage levels are safe and not a concern.
84
What is the activity of radiation?
Number of disintegrations per second of a source.
85
What is the method for correcting the count for background radiation when measuring the activity of a source?
Measure background radiation 3 times for 1 minute, take average.
Measure activity of source.
Take background count away from all readings.
86
What is an example of a radioactive element?
Radon
87
Where does most radioactive background activity come from?
Cosmic rays from space
Rock
Soil
88
What absorbs radioactive material from the soil?
Gas
Living things
Plants
89
What do gas, living things and plants do with the radioactive material they absorb?
Pass along food chain.
90
What are people who live in areas with high background radiation due to radon gas required to do?
Have homes be well ventilated to remove gas.
91
What human behaviour adds to background activity?
Medical x-rays
Radioactive waste from nuclear power stations
Radioactive fallout from nuclear weapon activity
92
What happens if radiation is incident upon a living cell?
Radiation can ionise cells which causes cellular damage.
If exposure high, can kill cell.
If exposure lower, can cause cancer.
Higher the exposure, higher the risk of cancer.
93
How can ionising radiation be used?
To kill cancer cells.
94
Why is alpha radiation not very dangerous if the radioactive source is outside the body?
Cannot pass through skin and unlikely to reach cells inside body.
95
When can alpha radiation damage cells in the body?
If radioactive source has been breathed in or swallowed.
96
Why is beta and gamma radiation dangerous even if the radioactive source is outside the body?
Can penetrate skin and cause damage to cells.
97
What are the steps that should be taken when handling radioactive sources to minimise the risk to the body?
Wearing protective clothing.
Keeping sortie as far away as possible by using tongs.
Being exposed to source for as short a time as possible.
Keeping radioactive materials in lead-lined containers.
98
What is a half-life?
Average time takes half atoms in radioactive element to decay.
99
What is special about radioactive decay?
Spontaneous process.
Cannot be controlled.
Not affected by temperature.
100
What are some of the uses of radioactivity in industry?
Radioactive isotopes used as traders to find out what is happening inside object without need to break into object.
Radioactive isotopes used to find route of underground pipes using gamma ray emitter.
Radioactive isotopes used to control thickness of metal as rolled into thin sheets.
101
What are some of the uses of radioactivity in medicine?
Gamma rays used to sterilise plastic objects such as syringes.
Different radioactive isotopes used to monitor functions of organs by injecting small amount into bloodstream an detecting emitted radiation.
102
What are some of the uses of radioactivity in homes?
Alpha radiation used in smoke alarms.
103
How is beta radiation used to control paper thickness in a mill?
Passed through paper and depending on how many particles able to pass through it, detector sends signal to control unit.
Control unit can adjusts how close rollers are to each other, adjusting thickness of paper back to normal.
104
How can radiation detect of fire?
Smoke alarms contain weak source of alpha radiation.
Alpha sources ionise air.
If smoke present, interacts with ions produced by particles and ionisation reduced.
Means less current flowing through air, causes alarm to sound.
105
What is nuclear fission?
Splitting of large atomic nucleus into smaller nuclei.
106
What is the process of nuclear fission (sample answer)?
1. Neutron fired towards nucleus.
2. Nucleus becomes unstable and splits.
3. 2 daughter nuclei + 2 or 3 fission neutrons produced.
4. Fission neutron can also go on to cause chain reaction.
107
What particles carry most of the energy from a nuclear fission reaction?
Fast moving neutrons (99% of energy).
108
What must happened to the neutrons before they can collide with a fresh uranium nuclei?
Need to be slowed down.
109
Where is the energy from fast moving neutrons passed on to in a nuclear reactor during nuclear fission?
Other components which use energy o heat water to drive turbines that turn generators.
110
What are the different parts contained in a fission reactor?
Nuclear fuel
Moderator (granite core)
Control rods
Coolant
Concrete shield
111
What is the function of the nuclear fuel in a fission reactor?
Fuel held in rods so when neutrons released during nuclear fission fly out, they cause nuclear fission in other rods.
112
What is the function of the moderator (graphite core) in a fission reactor?
Slows neutron down so more likely to be absorbed into nearby fuel rod.
113
What is the function of the control rods in a fission reactor?
Raised and lowered to stop neutrons from travelling between fuel rods and therefore change speed of chain reaction.
114
What is the function of the coolant in a fission reactor?
Heated ho by energy released from fission reactors and used to boil water to drive turbines in power station.
115
What is the function of the concrete shield in a fission reactor?
Daughter products of fission reaction are radioactive and can be hazardous so protects people from harmful radiation.
116
What are many of the features of a fission reactor designed to control?
Speed or reaction.
Temperature inside shielding.
117
What is an uncontrolled fission reaction the basis of?
Atomic bomb.
118
What are the advantages of nuclear power stations?
Produces no polluting gases.
Does not contribute to global warming.
Very low fuel costs.
Low fuel quantity reduces mining and transportation effects on environment.
High technology research required benefits other industries.
Power station has very long lifetime.
119
What are the disadvantages of nuclear power stations?
Waste is radioactive and safe disposal very difficult and expensive.
Local thermal pollution from waste water affects marine life.
Large-scale accidents can be catastrophic.
Public perception of nuclear power is negative.
Cost of building and safely decommissioning very high.
Cannot react quickly to change in electricity demand.
120
What is nuclear fusion?
When 2 small, light nuclei join together to make 1 heavier nucleus.
121
Where does nuclear fusion occur?
In stars where 2 hydrogen nuclei fuse together under high temperatures and pressure to form nucleus of helium isotope.
122
What is the equation for the simplest nuclear fusion reaction that happens in the Sun?
4 hydrogen nuclei > 1 helium nucleus
1 4
4 H > He
1 2
123
Wha this the combined mass of 4 hydrogen nuclei?
6.693x10-27^kg
124
What is the mass of 1 helium nucleus?
6.645x10-27^kg
125
What happens to the missing mass produced from nuclear fusion that happens in the Sun?
Converted into energy which radiates away from Sun.
126
What much energy does the Sun release every second?
3.8x1026^J
127
What is the issue with nuclear fusion?
Requires fusion of nuclei which are positive particles.
As 2 nuclei approach each other, repel each other as have same charge.
128
What conditions are required for nuclear fusion to take place?
Intense pressure and very high temperatures in order to force nuclei together and overcome electrostatic repulsion.
129
When has nuclear fusion been successfully achieved by scientists on Earth?
At JET experiment near Oxford but unable to create financially viable reactor.
