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Physics > Atomic Structure and Radioactivity > Flashcards

Atomic Structure and Radioactivity Flashcards

1
Q

how does the distance of the charged particles vary with the absorption or emission of electromagnetic radiation?

A
  • when atoms absorb electromagnetic radiation, the electrons at a particular level become ‘excited’ and can be pushed up to higher energy levels/ bigger distances from the nucleus
  • the emission of electromagnetic radiation would cause electrons to move closer to the nucleus, to a lower energy level
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2
Q

what is an isotope?

A

forms of an element that have the same number of protons (atomic number) but different numbers of neutrons (mass number)

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3
Q

what is an ion?

A

Electrically charged particle, formed when an atom or molecule gains or loses electrons

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4
Q

name the 5 scientists in order who made discoveries about the atomic model and when they made these discoveries

A
  1. dalton 1803
  2. thomson 1897
  3. rutherford 1909
  4. bohr 1913
  5. chadwick 1932
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5
Q

what did dalton discover about the atomic model?

A

1803- all matter is made of small particles called atoms and they are tiny spheres that can not be divided

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6
Q

what did thomson discover about the atomic model?

A

1897- discovered electrons and that the atom can be broken down, his plum pudding model was a ball of positive charge with negative electrons in it

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7
Q

what did rutherford discover about the atomic model?

A

1909- scattering experiment: positively charged alpha particles fired at gold foil bounced back meaning that the mass of the atom was concentrated in the nucleus and that the nucleus is positively charged, lead to nuclear model (atom with ball of positive charge in center and electrons floating around it)

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8
Q

what did bohr discover about the atomic model?

A

1913- electrons orbit the nucleus in shells and the nucleus contains protons

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9
Q

what did chadwick discover about the atomic model?

A

1932- discovered neutrons- he bombarded beryllium atoms with alpha particles and an unknown radiation was produced and he interpreted this radiation as being composed of particles with a neutral electrical charge and the approximate mass of a proton

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10
Q

what is the activity of a radioactive source?

A

the rate at which its unstable nuclei decay

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11
Q

what is the activity of a radioactive source measured in and by what?

A

measured in Becquerel (Bq) by a Geiger-Muller tube

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12
Q

what is the penetrating power through materials of an alpha particle?

A

and alpha particle can be absorbed by skin/ paper

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13
Q

what is the range in air of an alpha particle?

A

the range in air of an alpha particle is less than 5cm

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14
Q

what is the ionising power of an alpha particle?

A

alpha particles have a high ionising power

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15
Q

what is the penetrating power through materials of a beta particle?

A

a beta particle can be absorbed by 3mm of aluminium foil

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16
Q

what is the range in air of a beta particle?

A

the range in air of a beta particle is around 1 metre

17
Q

what is the ionising power of a beta particle?

A

a beta particle has very low ionising power

18
Q

what is the penetrating power through materials of a gamma ray?

A

a gamma ray can be absorbed by lead/ concrete

19
Q

what is the range in air of a gamma ray?

A

the range in air of a gamma ray is less than 1km

20
Q

what is the ionising power of a gamma ray?

A

gamma rays have very low ionising power

21
Q

what are the uses of gamma rays?

A
  • radiotherapy- beams of gamma rays can be used to kill cancerous tumours deep inside the body
  • medical tracers- injected radioactive sources that emit gamma radiation can be used as tracers to make soft tissues, such as blood vessels or the kidneys, show up through medical imaging processes- x-rays
22
Q

what is a use of alpha radiation?

A
  • in smoke detectors- it ionises air particles causing a current to flow and if smoke is prsent, it binds to the ions, stopping the current and the alarm goes off
23
Q

what is a use of beta radiation?

A
  • to test thickness of sheets of metal as they are not immediately absorbed by them like alpha but don’t penetrate as far as gamma so slight variations in thickness affect the amount of beta radiation that will pass through
24
Q

what is the arrangement of an alpha particle and how does it change the mass number and atomic number?

A

Alpha decay (two protons and two neutrons) changes the mass number of the element by -4 and the atomic number by -2 (-4 on top, -2 on bottom, He symbol or a symbol)

25
Q

what is the arrangement of a beta particle and how does it change the mass number and atomic number?

A

Beta decay changes the atomic number by +1 because it is an electron (0 on top, -1 on the bottom, e symbol or beta symbol)

26
Q

define half-life

A

half life is the time it takes for the number of unstable nuclei or count-rate of a radioactive isotope in a sample to halve

27
Q

how do you calculate half life?

A

depending on the question
* finding how much substance is left after a certain time- work out how many half-lives are in the time given and then calculate (1/2) to the power of how many half-lives it is and then put this as a ratio of the amount of substance: what is left
* finding the half-life- keep on halfing the number of Becquerels until you get to the number it says it got down to to find how many half-lifes the number drops by and then divide or times this to find one half life

28
Q

what are the hazards of contamination?

A

radioactive particles could get inside your body and is radioactive for as long as the source is on or in it but is very difficult to remove

29
Q

what is a hazard of irradiation?

A

exposing objects to beams of radiation can damage living cells but doesn’t make the object radioactive

30
Q

what precautions can be taken to protect against hazards from radioactive sources?

A
  • keep radioactive sources shielded in a lead-lined boxwhen not in use
  • wear protective clothing
  • avoid contact with bare skin
  • wear face masks to avoid breathing in materials
  • limit exposure time
  • handle radioactive materials with
    tongs in order to keep a safer distance from sources
31
Q

is contamination or irradiation more harmful? why?

A

contamination because it ccannot be removed easily and can get inside the body making it radioactive and causing internal harm

32
Q

what is the importance of peer-review when scientists share findings of studies into the effects of radiation on humans?

A

peer review is important to check if the study:
* Valid - does it measure what it says it does, was the method designed correctly and appropriately?
* Original - has anyone else already carried out similar research, and has their work been credited? Are the results new?
* Significant - are the findings of the research important?

33
Q

give some examples of natural and man-made background radiation

A
  • mainly radon gas in rocks in the ground (natural)
  • buildings (man-made)
  • cosmic rays from space (natural)
  • medical sources (man-made)
  • food
34
Q

what are two factors that could affect the level of radiation you are exposed to?

A

occupation and location

35
Q

what is the relationship between the instability and half-life of radioactive isotopes?

A

the longer the half-life, the more stable because it takes longer to decay

36
Q

why do the hazards associated with radioactive material differ according to the half-life involved?

A
  • because if a radioactive substance has a very long half-life, we know that it will remain radioactive for a very long time
  • the longer a substance remains radioactive, the more dangerous it is
37
Q

describe and evaluate the uses of nuclear radiation in exploration of internal organs and controlling/ destroying unwanted tissue?

A
  • exploring internal organs- medical tracers can be used to help diagnose problems but could have a small risk of damage to living cells/ tissue
  • controlling/ destroying unwanted tissue- radiotherapy is used to kill cancer cells but ultimately damages to some normal cells too, leaving the patient with side effects/ feeling ill
38
Q

describe nuclear fission

A
  • the splitting of a large nucleus to produce two smaller ones
  • two or three neutrons are also released in the process which then collide with other unstable nuclei, causing them to split= a chain reaction happens
  • this makes nuclear energy
39
Q

describe nuclear fusion

A
  • nuclear fusion is when two small, light nuclei join together to make one larger nucleus
  • since nucleuses are positive, they repel and are very unlikely to collide unless they are moving very fast with lots of energy
  • this happens in stars like the sun

Physics (27 decks)

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