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IGCSE Physics > atomic physics > Flashcards

atomic physics Flashcards

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1
Q

What does Rutherford’s nuclear model of an atom state

A
  • an atom consists of a positively charged centrally located nucleus which makes up almost the entire mass of the atom
  • it is surrounded by orbits filled with negatively charged electrons that remain in a circular path around the nucleus due to the strong electrostatic force of attraction between the positive nucleus and the negatively charged electrons
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2
Q

What are the observations and conclusions of the greiger-marsden alpha-particle scattering experiment

A

(through a thin gold foil)

  • the majority of particles go straight through without deflection (conclusion: this happens because majority of the space inside the atom is empty)
  • some are deflected at angles less than 90deg (conclusion: this is because there is a positive charge in the atom)
  • very few are deflected at angles greater than 90/backscattered
    (conclusion: the nucleus with positive charge takes up a very small space inside the atom)
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3
Q

what is nuclear fission

A

when large unstable nuclei break up into smaller nuclei and the process releases energy. This occurs in power stations

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4
Q

what is nuclear fusion

A

nuclear fusion takes place in stars like the sun and is the process in which smaller nuclei collide with each other at high speeds to form larger nuclei and release energy in the process.

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5
Q

what is a nuclear reaction

A

the nucleus reacts and we balance mass numbers and atomic numbers

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6
Q

what is background radiation

A

background radiation is always present in the environment around us

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7
Q

natural sources of background radiation

A

radioactive argon gas present in the atmosphere, radioactive rocks and minerals beneath the earth’s surface and background cosmic radiation from outer space

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8
Q

artificial sources of background radiation

A

uses of radioactive isotopes in medicine, radioactive waste from nuclear power stations and nuclear weapons

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9
Q

ways to detect radiation

A
  • photographic film
  • geiger-muller tube/counter (GM tube)
  • gold-lead electroscope
  • scintillation counters
  • spark counters
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10
Q

properties of radioactive emission

A
  • spontaneous: can occur without excitation or external factors
  • random: we do not know which radioactive atom is going to decay at a certain point of time but we know that a fixed proportion of atoms will decay in a period of time
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11
Q

what are alpha particles

A
  • consists of 2 protons and 2 neutrons

- essentially a helium nucleus

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12
Q

charge of alpha particles

A

2+

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13
Q

range of alpha particles in air

A

2cm

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14
Q

penetration of alpha particles

A

stopped by paper

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15
Q

ionization of alpha particles

A

high

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16
Q

what is a beta particle

A

a high speed electron

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17
Q

charge of beta particles

A

-1

18
Q

range of beta particles in air

A

few 10s of cm

19
Q

penetration of beta particles

A

stopped by few mm of aluminium

20
Q

ionization of beta particles

A

medium

21
Q

what are gamma rays

A

electromagnetic waves

22
Q

charge of gamma rays

A

0

23
Q

range of gamma rays in air

A

infinite

24
Q

penetration of gamma rays

A

reduced by few mm lead

25
Q

ionization of gamma rays

A

low

26
Q

deflection of gamma rays in electrical field

A

passes straight through

27
Q

deflection of alpha radiation in electric field

A

deflected towards negatively charged plate

28
Q

deflection of beta radiation in electric field

A

deflected towards positively charged plate

29
Q

deflection of gamma radiation in magnetic fields

A

gamma radiation passes straight through without any deviation

30
Q

deflection of alpha and beta radiation in magnetic fields

A
  • both deflected in opposite directions (which can be found using Flemings left hand rule)
  • beta particles deflect more than alpha particles as they are much lighter
31
Q

what is ionisation

A

the process by which electrons are removed or added to a substance by applying energy

32
Q

why does alpha ionise the most

A

-greater mass and charge

33
Q

why do alpha particles have the shortest range

A
  • they ionise virtually every atom they pass

- so they lose energy quickly and have a short range

34
Q

why do beta particles have a moderate range

A
  • the particles create a less dense trail of ions than alpha, and consequently have a longer range
  • they tend to be more dangerous than alpha because they are able to travel further and penetrate skin yet are still ionizing enough to cause damage
35
Q

why do gamma rays have unlimited range

A

they are the least ionizing form of radiation

36
Q

common uses of radiation

A
  • controlling thickness of material
  • medical tracers to detect blood clots
  • industrial tracers to detect leaks in pipes
  • cancer treatment
  • sterilization
  • smoke detectors
37
Q

what is radioactive decay

A

-occurs due to the presence of unstable nuclei in some isotopes, as a result they emit radiation to become stable

38
Q

alpha/beta radiation in radioactive decay

A

affects the composition of the nucleus and changes to that of a different element

39
Q

gamma radiation in radioactive decay

A

does not affect the composition of the nucleus and is released only after alpha or beta emission to get rid of excess energy in the nucleus

40
Q

what is the half life of an isotope

A

the time taken for the number of original nuclei to drop to half of its initial value/the time taken for half a radioactive substance to decay (can be found from a nuclide graph)

41
Q

what can radioactive radiation cause to living cells

A
  • mutations
  • breed cancerous cells
  • may kill living cells
42
Q

safety precautions for radioactive radiation

A
  • store the sources in lead-lined boxes
  • minimise the amount of time you handle sources for and return them to their boxes as soon as you have finished using them
  • stay at a safe distance from the radioactive source
  • when handling sources do so at an arm’s length, using a pair of tongs or forceps and other source-handing tools
  • wear protective clothing

IGCSE Physics (12 decks)

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