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GCSE Physics > Atomic Structure > Flashcards

Atomic Structure Flashcards

1
Q

What is the radius of an atom?

A

About 1 × 10-10 metres

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2
Q

What is the basic structure of an atom composed of?

A

A positively charged nucleus composed of protons and neutrons surrounded by negatively charged electrons

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3
Q

What is the relationship between the radius of a nucleus and an atom?

A

The radius of a nucleus is less than 1/10,000 of the radius of an atom

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4
Q

Where is most of the mass of an atom concentrated?

A

In the nucleus

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5
Q

How do electron arrangements change in an atom?

A

With the absorption or emission of electromagnetic radiation

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6
Q

In an atom, what is the relationship between the number of electrons and protons?

A

The number of electrons is equal to the number of protons

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7
Q

What is the overall electrical charge of an atom?

A

Atoms have no overall electrical charge

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8
Q

What does the atomic number represent?

A

The number of protons in an atom of an element

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9
Q

What is the mass number of an atom?

A

The total number of protons and neutrons in an atom

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10
Q

What are isotopes?

A

Atoms of the same element with different numbers of neutrons

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11
Q

What happens to atoms when they lose one or more outer electron(s)?

A

They turn into positive ions

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12
Q

What can lead to a scientific model being changed or replaced?

A

New experimental evidence

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13
Q

What was the belief about atoms before the discovery of the electron?

A

Atoms were thought to be tiny spheres that could not be divided

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14
Q

What did the plum pudding model suggest about the atom?

A

The atom is a ball of positive charge with negative electrons embedded in it

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15
Q

What conclusion was drawn from the alpha particle scattering experiment?

A

The mass of an atom is concentrated at the center (nucleus) and the nucleus is charged

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16
Q

Who adapted the nuclear model of the atom?

A

Niels Bohr

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17
Q

What did Bohr suggest about electrons?

A

Electrons orbit the nucleus at specific distances

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18
Q

What name was given to the smaller particles that make up the positive charge of the nucleus?

A

Proton

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19
Q

Who provided evidence for the existence of neutrons?

A

James Chadwick

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20
Q

Fill in the blank: The _______ model was replaced by the nuclear model.

A

plum pudding

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21
Q

True or False: The theoretical calculations of Bohr disagreed with experimental observations.

A

False

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22
Q

What were the results of the alpha particle scattering experiment and what the conclusions of this?

A
  1. Most of the alpha particles did pass straigt through the foil - the atom is mostly empty space.
  2. A small number of alpha particles were deflected by large angles (>4 degrees) as they passed through the foil - evidence that there is a concentration of postiive charge (two positive charges repel each other, so the alpha particles were deflected)
  3. A very small number of alpha particles came straight back off the foil - the positve charge and mass are concentrated in a tiny volume in the atom, so the chance of being on that exact collision course was very small.

NB: Alpha particles never hit the nucleus - they are only deflected by the nucleus.

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23
Q

What is radiation?

A

Radiation is the emission or transmission of energy in the form of waves or particles through space of through material medium.

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24
Q

What is the process called when unstable atomic nuclei give out radiation to become more stable?

A

Radioactive decay

This process is random in nature.

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25
Q

What is activity?

A

The activity of a radioactive source is the number of nuclei decaying per second in the source.

Activity is measured in becquerel (Bq).

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26
Q

How is count-rate defined in the context of radioactive decay?

A

The number of decays recorded each second by a detector

An example of a detector is a Geiger-Muller tube.

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27
Q

What consists of two neutrons and two protons and is the same as a helium nucleus?

A

Alpha particle (α)

Alpha particles are a type of nuclear radiation emitted during decay.

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28
Q

What type of particle is a high-speed electron ejected from the nucleus?

A

Beta particle (β)

This occurs when a neutron turns into a proton.

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29
Q

What is electromagnetic radiation emitted from the nucleus called?

A

Gamma ray (γ)

Gamma rays are another form of nuclear radiation.

30
Q

What type of nuclear radiation is simply a neutron?

A

Neutron (n)

Neutrons can also be emitted during radioactive decay.

31
Q

Why may an atom be unstable?

A

There could be:
too many protons
too many neutrons
too much energy

32
Q

What is the radioactivity of a material?

A

The radioactivity of a material is the rate that it emits radiation.

33
Q

What part of the atom does radioactivity ALWAYS come from?

A

the nucleus!! - never anywhere else - if it’s not from the nucleus, it is not radioactivity

34
Q

What is alpha radiation and what are its properties?

A

An unstable nucleus emits a group of 2 protons and 2 neutrons.
This is called an alpha particles
The mass is 4 atomic mass units.
The charge is +2 units of charge.
It’s travelling fast (at 10% speed of light)
It carries charge, mass and energy aqay from the nucleus.
It’s identical to the nucleus of a helium atom.
Has no electrons.

35
Q

What is beta radiation and what are its properties?

A

An unstable nucleus emits an electrons
This is called a beta particle
Its mass is negligible (1/2000)
It’s charge is -1
It’s travelling really fast (1/2 speed of light)
It carries charge and energy aqay from the nucleus, but essentially no mass
(basically a neutron turns into an electron and a proton - that’s how beta radiation happens)

36
Q

What is gamma radiation and what are its properties?

A

An unstable nucelus emits high-energy electromagentic radiation
This is called a gamma ray
It has no mass
It has 0 charge
It’s travelling at the speed of light (3x10^8 m/s)
It carries only energy aqay from the nucles 0 nothing else

37
Q

What is neutron emission?

A

Neutrons are emitted - makes nucleus more stable

38
Q

What is ionising radiation?

A

Ionising radiation is any radiation which causes an atom to be ionised. This ca be alha, beta, gamma and x-rays.

39
Q

How is ionising radiation cause?

A

They cause atoms to be ionised by crashing into an atom’s orbital electrons, and knocking them off their orbits, leaving an atom behind with too few electrons, i.e an ion

40
Q

True or false - X-rays are ionising radiation and radioactive

A

FALSE - They are a type of high energy light, or electroamgnetic radiation. They are ionising radiation, but not radioactivity, because they come from the electrons around an atom, not from the nucelus, which is where all radioactivity comes from.

41
Q

What is the nature of radioactive decay?

A

Random

Radioactive decay occurs without any predictability in the timing of individual decay events.

42
Q

What is the half-life of a radioactive isotope?

A

The time it takes for the half of radioactive nuclei in a sample to decay

It can also be defined as the time for the count rate from a sample to fall to half its initial level.

43
Q

Fill in the blank: The half-life of a radioactive isotope is the time it takes for the number of nuclei of the isotope in a sample to _______.

A

halve

44
Q

What does the term ‘count rate’ refer to in the context of radioactive decay?

A

The activity from a sample containing the isotope

It reflects the number of decay events occurring in a given time frame.

45
Q

What are the penetrating properties of alpha, beta and gamma radiation?

A

Alpha radiaiton:
strongly ionising
range in air is ~ 5cm
Penetration - stopped by paper or skin
Strongly causes ionisation
Is dangerous if consumed/inhaled (internal exposure)

Beta radiation:
Weakly ionising
Range in air is ~1m
Penetration - stopped by a few mm of aluminium
Is dangerous

Gamma radiation:
Very weakly ionising
Range in air is ~ 1km
Penetration - almost stopped by a few cm of lead
Is dangerous

46
Q

Give 2 safety precautions the teacher should have taken in a demonstration involving radiation.

A

PPE - gloves, apron etc.
Wearing (goggles)/safety glases
Minimising time wiht the radioactive material
Keep at a distance from the source
Hold the source with tongs

47
Q

How does a geiger counter work?

A
48
Q

What are the different uses of radioactiviy?

A

Medical radioactive tracers
Cancer treatment
industrial radioactive tracers
sterilsing food + medical equipment
Thickness control
Smoke detector

49
Q

How do smoke detectors work?

A
50
Q

What is irradiation?

A

Irradiation is the exposure of objects ot radiation. It can damage cells.

51
Q

What are the uses of irradiation?

A

sterlisation of hosptial equippment
Sterlisation of food
Delay/prevention of food spoiling

52
Q

True or false - Irradiation does not make food radioactive.

A

TRUE - IRRADIATION DOES NOT MAKE FOOD RADIOACTIVE

53
Q

What is contamination?

A

Contamination is the unwanted presence of radioactive isotopes on an object.
The radioactive isotopes does make the contaminated object radioactive.

54
Q

What is the difference between contamination and irradiation?

A
55
Q

What is background radiation?

A

Background radiation is a naturally occuring radiation. It is a measure of the level of ionising radiation present in the environmnent at a particular location which is not due to deliberate introduction of radiation sources.

56
Q

What is nuclear fallout?

A

Nuclear fallout

57
Q

Where does background radiation come from?

A

Can come from natural sources:
Radon gas from the ground (50%)
Rocks in the ground
Cosmic rays (12%)
Food and drink (9.5%)

Can come from man-made sources:
Medical (15%)
Gamma rays from the ground and buildings (13%)
Fallout from nuclear weapons testing and nuclear accidents

58
Q

What is radiation dose measured in?

A

sieverts (Sv)
1000 millisieverts (mSv) = 1 sievert

59
Q

What is nuclear fission?

A

Nuclear fission si the splitting of a large atomic nucleus into smaller nuclei, and two or three neutrons.

60
Q

What is the process of nuclear fission (using uranium-235 as an example?

A
  1. A uranium-235 nucleus absorbs a neutron
  2. For an instant it becomes a uranium-236 nucleus, which is unstable.
  3. It then rapidly decays into to two lighter nuclei and two or three neutrons.
  4. The fission process releases a gret amount of energy in teh form of gamma radiaiton and heat.
61
Q

What is a chain reaction?

A

A nuclear chain reaction occurs when a neutron splits a nucleus, releasing more neutrons, which in turn go on to split even more nuclei.

62
Q

How does nuclear fission lead to a chain reaction?

A

Neutrons released in a fission reaction collide with other nuclei causing further fission reaction.
NB: theres only 1 chain reaction, but they consist of any individual fission reactions.

63
Q

What is critical mass?

A

Critical mass is the minimum mass of fissionable material needed to start a chain reaction.

64
Q

What is the scientific method?

A
  1. Observations
  2. Proposing a theory/ideas/hypotheses
  3. Experiments
  4. Collect data
  5. Compare theories/ideas/hypotheses with the experimental data/results
65
Q

If a theory/idea/hypothesis agrees with the data, we say what?

A

The idea is supported by the experiment.
The experiment provides evidence for the idea.

NEVER PROVES THE IDEA/THEORY/HYPOTHESIS

66
Q

If a theory/idea/hypothesis disagrees with the data, we say what?

A

The idea is disproved
The idea is inconsistent with the evidence.

67
Q

What is peer review?

A

Peer review is hte independent assessment of your research by experts in your field.

68
Q

What are the different parts of a nuclear fission reactor?

A

Nuclear fuel: radioactive materials, usually uranium or plutonium are used in nuclear fission reactors.

Graphite core (moderator): slows down the neutrons in a nuclear fission reactor

Control rods: the control rods are used to absorb excess neutrons and control the rate of the nuclear fission reaction.

Coolant: a liquid that is used to transfer thermal energy within a system.

Concrete shield: the daughter products of a nuclear fission reaction can be a hazard.

69
Q

What are the processes inside a nuclear plant?

A

Nueclear fission reaction heats water to make steam, which turns turbines, which turns generators, which produces electricity.

70
Q

What is nuclear fusion?

A

two small/light nuclei join together to form a single heavier nucleus, releasing large amounts of energy.

71
Q

What is necessary for fusion reactors?

A

Very high temperatures and very high pressures, in order to overcome the electrostatic force of repulsion between the two nuclei to fuse together.

GCSE Physics (6 decks)

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