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Atomic Structure Flashcards

1
Q

Give an approximation for the radius of an atom

A

1x10 -10

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2
Q

What are the three subatomic constituent of an atom?

A

Protons, neutrons, electron

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3
Q

Where is the most of the mass of an atom concentrated?

A

In the nucleus

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4
Q

Approximately what proportion of the total radius of an atom is the radius of the nucleus?

A

1/10,000

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5
Q

Describe the arrangement of protons, neutrons and electrons in an atom

A

The protons and neutrons are found in the atoms nucleus
Electrons are found in a discrete energy levels around the nucleus

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6
Q

What type of charge does the nucleus of an atom have and why

A

Positive charge, the nucleus contains protons and neutrons
Protons have a positive charge
Neutrons have no charge

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7
Q

Give two ways, an atom electric arrangement can be changed

A

Absorbing electromagnetic radiation
Emitting electromagnetic radiation

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8
Q

Explain how an atom is electric arrangement changes when it absorbs an EM radiation

A

Electrons move further away from the nucleus
Move to a higher energy level

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9
Q

Explain how an atoms electron arrangement changes when it emits em radiation

A

Electrons move closer to the nucleus
They move to a lower energy level

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10
Q

What do all forms of the same element have in common?

A

They all have the same number of protons?

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11
Q

What is the name given to the number of protons in an atom?

A

Atomic number

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12
Q

What is an atoms mass number?

A

The total number of protons and neutrons in the atom

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13
Q

What is an isotope of an atom?

A

And atom of an element that has a different number of neutrons, but the same number of protons

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14
Q

How do atoms turn into positive ions

A

They lose one or more of the outer electrons
Electrons or negatively charged to the resultant charge of the atom is positive

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15
Q

What may lead to a scientific model been changed or replace?

A

The discovery of a new experimental evidence, which doesn’t agree with existing theory

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16
Q

How does the plum pudding model describe the atom?

A

A ball a positive charge, with negatively charged electrons, distributed evenly throughout

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17
Q

Prior to the discovery of the electron, what was believed about the atom

A

The atom was believed to be indivisible

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18
Q

Which experiment led to the plum pudding model being discarded

A

Rutherford is alpha scattering experiment

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19
Q

What is the name given to the currently accepted model of the atom?

A

The bohr nuclear model

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20
Q

State the conclusions of the alpha scattering experiment

A

Most of the mass of the atom is concentrated at the centre in the nucleus, the nucleus positively charge

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21
Q

What did James Chadwick’s experiment on the atom prove

A

The existence of neutrons

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22
Q

Why do unstable nuclei give out radiation?

A

Unstable, nuclei undergo decay to become more stable
As they release radiation, the stability increases

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23
Q

What is the name of the process in which an unstable nucleus gives out radiation to become more stable

A

Radioactive decay

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24
Q

Define the activity of an unstable nucleus

A

Activity is the rate of decay of a source of unstable nuclei

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25
What is the count rate?
The number of radioactive decay per second for a radioactive source
26
Give an example of a detector that may be used to measure count rate
Geiger-Müller tube
27
What are the consiituentsof an alpha particle?
Two. Protons and two neutrons It is the same as a helium nucleus
28
Which type of radiation is most ionising?
Alpha
29
Which type of radiation is least ionising
Gamma
30
Stay any changes to a mass or charge occur due to the emissions of a gamma ray
 Both mass and charge remain unchanged
31
Describe the nature of radioactive decay
Random Which nuclei decay is an when is determined only by chance It is impossible to predict which new nuclei will decay, and when
32
Define the half life of a radioactive isotope
The time it takes for the number of unstable nuclei in a substance to half The time it takes for the count rate from a sample to fall to half its initial level
33
What is radioactive contamination?
The presence of unwanted radioactive nuclei of the materials
34
What is irradiation?
The process of exposing a material to nuclear radiation The material does not become radioactive
35
Give four sources of background radiation
Rocks Cosmic rays from space Nuclear weapon testing Nuclear accidents
36
How should background radiation be dealt with in calculations?
The background count should be subtracted from any readings before calculations are attempted
37
What is the unit used to measure radiation dosage?
Sieverts (Sv)
38
How many millisievert equal to 1 sievert
1000 millisievert= 1 sievert
39
Why might the radiation doses that different people experience differ
Some occupations involve working with radiation Background radiation difference with location due to things such as the locality of nuclear power station or radiation related testing
40
What factor determines how dangerous is a particular radioactive isotope is?
The half life of the isotope
41
Why are isotopes of long half life particular harmful?
They remain radioactive much longer periods of time They must be stored in specific ways to avoid humans and the environment from being exposed to radiation for too long
42
Give two uses of nuclear radiation in the field of medicine
Examining of internal organs Controlling and destroying unwonted tissue
43
How is radiation used in sterilisation?
Gamma emmiters are used to kill bacteria on equipment
44
Explain the process of radiotherapy
Gamma emmiters direct gamma rays at the cancer cells The cancerous cells absorb radiation and are killed
45
How are medical traces chosen?
They should have short half life and decay into a stable isotope which can be excreted They should only release gamma radiation since it is weekly ionising, and can easily pass through body tissue without damaging it
46
What is the nuclear fission?
The splitting of a large, unstable, nuclei to form a smaller, more stable nuclear. The emissions of a spare neutron
47
Give an example of a fissionable isotope
Urainium 235
48
Give an example of a fissionable isotope
Urainium 235
49
What usually needs to happen to induce fission
The unstable, nuclei must absorb a neutron Spontaneous fission is rare
50
Alongside two smaller nuclei, what else is emitted in a fission reaction?
Two or three neutrons Gamma rays Energy
51
What form of energy do all fission products have?
Kinetic energy
52
What takes place during a chain reaction in a nuclear reactor
An unstable nucleus absorbs, a neutron The nucleus, undergoes fission and releases two or three further neutrons These induce more fission which results in a chain reaction
53
What is the consequence of an uncontrolled chain reaction?
The rate of fission events become to a high in results in the production of too much energy This can lead to nuclear explosion
54
What are three main components of the core a nuclear reactor
Fuel rods, control rods, moderator
55
What is the role of the moderator in a nuclear reactor?
To slow down the neutron, so they are travelling at speed, which allows them to be absorbed by fissile nuclei and cause fission
56
How is the chain reaction in a fission reactor kept under control?
Control rods are positions in between the fuel rods The rate of fission is controlled by moving the rods up and down The lower, the rods are inserted, to slow the rate of fission
57
What term is used to describe nuclei, in which fission can be induced through the absorption of slow neutrons
Fissile nuclei
58
What is nuclear fusion?
The joining up two light nuclei to produce a heavier, nuclei and release energy
59
Name two isotopes of hydrogen which are commonly used in nuclear fusion
Deuterium tritium
60
Which releases more energy nuclear fission and nuclear fusion
Nuclear fusion
61
Explain the difficulty of generating energy through nuclear fusion
Fusion requires very high temperatures, which in itself requires large quantities of energy and also requires casing which can withstand them
62
Explain my nuclear fusion is currently not a viable way to produce energy on Earth
With current equipment/techniques, the energy required is greater than energy produced, resulting in the net energy loss

physics (9 decks)

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