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Physics iGCSE > P8 - Atomic Physics > Flashcards

P8 - Atomic Physics Flashcards

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1
Q

An atom

A

a small positive nucleus, surrounded by negative electrons

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2
Q

Ion

A

An ion is an electrically charged atom or group of atoms formed by the loss or gain of electrons

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3
Q

Stable atom

A

One that has the same number of protons and electrons and is normally electrically neutral

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4
Q

Positive ion

A

Atoms which have lost electrons: more protons than electrons

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5
Q

Negative ion

A

Atoms which have gained electrons: more electrons than protons

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6
Q

Proton number, Z

A

The number of protons in an atom (also called the atomic number)
* dictate the order of the elements in the periodic table
* also equal to the number of electrons - in order to have no overall charge

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7
Q

Nucleon number, A

A

Total number of particles in the nucleus (also called mass number)
* number of prtons + number of neutrons

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8
Q

Nuclide notation (ZXA)

A
  • Top number A - nucleon/mass number
  • Bottom number Z - proton number
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9
Q

Nuclide

A

A nuclide is a group of atoms containing the same number of protons and neutrons

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10
Q

Isotope

A

Isotopes are atoms of the same element that have an equal number of protons but a different number of neutrons
* tend to be more unstable due to this imbalance and are more likely to decay

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11
Q

Charge of proton, neutron and electron

A
  • Proton: +1
  • Neutron: 0
  • Electron: -1
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12
Q

Relative atomic mass of proton, neutron, electron

A
  • Proton: 1
  • Neutron: 1
  • Electron: 1/2000
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13
Q

Nuclear charge

A

The relative charge of the nucleus
* The term ‘relative’ refers to the charge of the particle divided by the charge of the proton
* So, proton number determines relative charge

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14
Q

Nuclear fission

A

The splitting of a large, unstable nucleus into two smaller nuclei

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15
Q

Nuclear fusion

A

When two light nuclei join to form a heavier nucleus

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16
Q

Background radiation

A

The radiation that exists around us all the time

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17
Q

Natural sources of background radiation (name and explain 3)

A
  • Radon gas (in the air)
    • airborne radon comes from the ground from the natural decay of uranium in rocks and soil
    • tasteless, colourless and odorless but unhealthy
  • Rocks and Buildings
    • decay of heavy radioactive elements such as uranium and thorium which occur naturally in rocks
  • Cosmic rays from space
    • collision of protons from the sun with molecules in the Earth’s air lead to gamma radiation production
    • also can come from supernovae
  • Carbon-14 biological material
    • all organic material contain it but constantly replace the supply of carbon in their system leaving its amount constant
  • Radioactive material in food and drink
    • naturally occuring radioactive elements can get into food and water since they are in contact with rocks and soil
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18
Q

Man made sources of background radiation (name and explain 3)

A
  • Medical resources
    • Used in X-rays, CT scans, tracers and radiation therapy
  • Nuclear waste
    • Does not contribute much to it, it can still be dangerous to the people handling it
  • Nuclear fallout from nuclear weapons
    • The residue radioactive material that is thrown into the air after a nuclear explosion
    • Presently low in general but would increase significantly in areas where nuclear weapons are tested
  • Nuclear accidents
    • Though are extremely rare, the can be catastrophic and contribute a large dose of radiation into teh atmosphere
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19
Q

Dose

A

The amount of radiation received by a person is called the dose

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20
Q

Count rate

A

Count rate is the number of decays per second recorded by a detector and recorded by the counter (measured in counts/s or counts/min)
* decreases the further the detector is from the source - radiation becomes more spread out

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21
Q

Geiger-Müller cube

A

The Geiger-Müller tube is the most common device used to measure and detect radiation
* each time it absorbs radiation, it transmits an electrical pulse to a counting machine which makes a clicking sound or displays the count rate
* greater click frequency suggests higher radiation
* lower count, the further away from source

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22
Q

Examples of radiation detectors (name 3)

A
  • Geiger-Müller tube
  • Photographic film
  • Ionisation chambers
  • Scintillation counters
  • Spark counters
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23
Q

Why are some atomic nuclei unstable?

A
  • Because of an imbalance in the forces within the nucleus
  • Some isotopes are unstable because of their large size or because they have too many or too few neutrons
24
Q

How can unstable nuclei become more stable?

A

Emit radiation
* can be in the form of a high energy particle or wave
* as the radiation moves away from the nucleus it takes some energy with it which reduces the overall energy of the nucleus

25
Q

Radioactive decay

A

The process of emitting radiation is called radioactive decay
* it is a random, unpredictable process

26
Q

What does the randomness of radioactive decay mean? (name 3 qualities)

A
  • There is an equal probability of any nucleus decaying
  • It cannot be known which particular nucleus will decay next
  • It cannot be known at what time a particular nucleus will decay
  • The rate of decay is unaffected by the surrounding conditions
  • It is only possible to estimate the probability of a nuclei decaying in a given time period
27
Q

Two properties of radiation

A
  • spontaneous
  • random in direction
28
Q

Three types of radiation

A
  • Alpha (α) particles
  • Beta (β-) particles
  • Gamma (γ) radiation
29
Q

Describe alpha particles

A
  • Symbol: α
  • It is the same as a helium nucleus
    • because it consists of two neutrons and two protons
  • Have a charge of +2 and so can be affected by an electric field
30
Q

Describe beta particles

A
  • Symbol: β-
  • Fast moving electrons
  • Produced in the nuclei when a neutron changes into a proton and a neutron
  • Have a charge of -1 so they can be affected by an electric field
31
Q

Describe gamma rays

A
  • Symbol: γ
  • Are electromagnetic waves
  • Have the highest energy of the different types of electromagnetic waves
  • Have no charge
32
Q

Charge of three radioactive particles

A
  • Alpha: +2
  • Beta: -1
  • Gamma: 0
33
Q

Range of three radioactive particles

A
  • Alpha: few cm
  • Beta: few 10s of cm
  • Gamma: ifinite
34
Q

Penetration of three radioactive particles

A
  • Alpha: stopped by paper
  • Beta: stopped by few mm of aluminium
  • Gamma: reduced by few mm of lead
35
Q

Ionisation of three radioactive particles

A
  • Alpha: high
  • Beta: medium
  • Gamma: low
36
Q

Ionisation

A

Ionisation is the process of which an atom becomes negative or positive by gaining or losing electrons

37
Q

Ionisation of alpha particles

A

Alpha is by far the most ionising form of radiation
* leave dense trail of ions behind them because of this they quickly lose energy and have a short range
* short range makes them relatively harmless if handled carefully but can be dangerous if the alpha emitter enters the body

38
Q

Ionisation of beta particles

A

Beta particles are moderately ionising
* create less dense trail of ions, have a longer range
* more dangerous than alpha because they are able to travel further and penetrate the skin

39
Q

Ionisation of gamma rays

A

Gamma is the least ionising form of radiation (although it is still dangerous)
* don’t produce as many ions, they are more penetrating and have a greater range
* can make them hazardous in large amounts

40
Q

What does ionising effects depend on?

A
  • The kinetic energy of the type of radiation: the higher the kinetic energy of the radiation, the more ionising it is
    * alpha has the greatest mass, gamma has virtually no mass
  • The charge: the greater the charge of the radiation, the more ionising it is
41
Q

Parent and daughter nucleus

A

During α-decay or β-decay, the nucleus changes to a different element
* The initial nucleus is called the parent nucleus
* The nucleus of the new element is called the daughter nucleus

42
Q

Alpha decay (and equation)

A

Alpha symbol added to element (remember this is a new element) with a 4 as the mass number (top) and two as proton number (bottom)
* Mass number decreases by 4
* Atomic number decreases by 2

43
Q

Beta decay (and equation)

A

Beta symbol added to completely new element with 0 as mass number (top) and -1 as atomic number (bottom)
* a neutron changes into a proton and an electron, e is emitted and p remains in nuclei
* mass number stays the same
* atomic number increases by 1

44
Q

Gamma decay

A

Gamma symbol added to the same element
* ray is emitted from an unstable nucleus which lessens its enegry but does not change its structure
* no change in mass number
* no change in atomic number

45
Q

Half-life

A

The time taken for half the nuclei of that isotope in any sample to decay
* it is constant for a particular isotope to decrease from 100% to 50% to 25% etc.

46
Q

How to calculate the half-life froma sample in a graph? (4 steps)

A
  1. Check the original activity (where the line crosses the y-axies)
  2. Halve this value and look for this activity
  3. Go across from the halved value (on the y-axis) to the best fit curve, and then straight down to the x-axis
  4. The point where you reach the x-axis should be the half-life
47
Q

Uses of radiation (name 4)

A
  • Medical procedures including diagnosis and treatment of cancer
  • Sterilising food (irradiating food to kill bacteria)
  • Sterilising medical equipment (using gamma rays)
  • Determining the age of ancient artefacts
  • Checking the thickness of materials
  • Smoke detectors (alarms)
48
Q

How is radiation used in smoke detectors?

A
  • Alpha particles are used in smoke detectors
  • The alpha radiation will normally ionise the air within the detector, creating a current
  • The alpha emitter is blocked when smoke enters the detector
  • The alarm is triggered by a microchip when the sensor no longer detects alpha
49
Q

How is radiation used in measuring the thickness of materials

A

Beta particles can be used for tracing and gauging thickness
* As material moves above the beta source, the particles are able to penetrate it can be monitored using a detector
* If the material gets thicker, more particles will be absorbed, meaning that less will get through
* If the material gets thinner the opposite happens

50
Q

How is radiation used in diagnosis and treatment of cancer?

A

Gamma rays can be used in radiotherapy
* They are directed at the cancerous tumour and are moved around to minimise harm to healthy tissue whilst being aimed at the tumour and kill its cells

51
Q

How is radiation used in sterilising food and medical equipment?

A

Gamma rays are used widely to sterilise medical equipment
* It is the most suitable because:
* It is the most penetrating out of all the types of radiation
* It is penetrating enough to irradiate all sides of the instruments
* Instruments can be sterilised without removing the packaging

52
Q

How can ionising radiation cause damage? (4)

A
  • Cell death
  • Tissue damage
  • Mutations
  • Cancer
53
Q

What can acute radiation exposure cause?

A
  • It can cause skin burns, similar to severe sunburn
  • Radiation can reduce the amount of white blood cells in the body, making a person more susceptible to infections by lowering their immune system
54
Q

How to handle radioactive sources safely (for students)? (name 4)

A
  • Keep the source in a lead lined container until the time it is needed
  • Use tongs to move the source, rather than handling it directly
  • The source should be kept at as far a distance from the student as possible during the experiment
  • The time that the source is being used should be minimised
  • After the experiment the student should wash their hands
  • The date and the time that the radiation has been used for should be recorded
55
Q

How is radioactive waste disposed of?

A

Radioactive waste with a long half-life is buried underground to provenet it from being released into the environment

Physics iGCSE (6 decks)

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