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Master Combined Science - Physics (Foundation) > Combined Physics - 6.4 > Flashcards

Combined Physics - 6.4 Flashcards

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1
Q

What is the size of an atom?

A

Very small – a radius of about 1x10-10 m

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2
Q

Describe the basic structure of an atom

A

A positively charged nucleus (protons and neutrons) orbited by negatively charged electrons

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3
Q

What is the radius of the nucleus

A

1/10’000th the radius of an atom (but contains most of the mass)

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4
Q

Describe electrons within energy levels

A

Electrons are arranged at different distances (energy levels) from the nucleus

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5
Q

How can electron arrangements change?

A
  • Absorption of electromagnetic radiation (higher energy level)
  • Emission of electromagnetic radiation (lower energy level)
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6
Q

What is the overall electrical charge of an atom?

A

No overall charge – electron and proton numbers are equal

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7
Q

How many protons do an atom of the same element have?

A

The same number

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8
Q

What is the atomic number?

A

The number of protons in an atom

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9
Q

What is the mass number?

A

The number of protons and neutrons in an atom

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10
Q

Draw the modern model of an atom

A
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11
Q

What is an isotope?

A

Atoms of the same element with different numbers of neutrons

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12
Q

What happens to an atom if it loses one or more outer electron(s)?

A

It becomes a positive ion

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13
Q

Before the discovery of the electron, what were atoms thought to be (as suggested by Dalton)?

A

Tiny spheres that could not be divided

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14
Q

What was the Plum Pudding model?

A

The atom was suggested to be a ball of positive charge with negative electrons embedded in it

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15
Q

What did Rutherford’s scattering experiment show?

A

The mass of the atom was concentrated in the centre (nucleus) and it was charged

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16
Q

How did Bohr adapt the nuclear model as suggested by Rutherford?

A

Bohr suggested electron orbit the nucleus at specific distances (energy levels)

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17
Q

What can the positive charge of a nucleus be subdivided into?

A

Protons

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18
Q

20 years after the nucleus became scientifically accepted, what did James Chadwick identify?

A

Neutrons (explaining the imbalance between atomic number and atomic mass)

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19
Q

Some atomic nuclei are unstable – what can the nucleus emit (and in doing so become more stable)?

A

Radiation – a random process of radioactive decay of the unstable nuclei

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20
Q

What is ‘activity’ in terms of nuclear radiation?

A

The rate at which a source of unstable nuclei decays

21
Q

How is nuclear ‘activity’ measured?

A

In becquerels (Bq) where 1 Bq is 1 decay per second

22
Q

What can a Geiger-Muller tube record?

A

The count-rate (the number of radiation decays reaching the device per second)

23
Q

What types of ionising nuclear radiation are there?

A
  • Alpha
  • Beta
  • Gama
24
Q

Describe alpha (α) radiation (structure, penetration, absorption and ionising strength)

A
  • 2 neutrons and 2 protons (like a helium nucleus)
  • They don’t penetrate very far (a few cm in air) and are absorbed by a piece of paper
  • They are strongly ionising
25
Q

Describe beta (β) radiation

(structure, penetration, absorption and ionising strength)

A
  • A fast moving electron (virtually no mass)
  • Penetrate a few metres in air and are absorbed by a 5mm sheet of aluminium
  • Moderately ionising
26
Q

Describe gamma (γ) radiation

(structure, penetration, absorption and ionising strength)

A
  • Waves of electromagnetic radiation
  • Penetrate far into materials and are absorbed by thick sheets of lead or metres of concrete
  • Weakly ionising
27
Q

As well as alpha, beta and gamma radiation what else can radiative substances release?

A

Radioactive substances can release neutrons (as they rebalance their atomic and mass numbers)

28
Q

What can nuclear equations represent?

A

Radioactive decay

29
Q

How can an alpha particle be represented?

A
30
Q

How can a beta particle be represented?

A
31
Q

What can nuclear radiation emission change in a nucleus?

A

The mass or the charge

32
Q

What happens to Rn219 when it experiences alpha decay?

A

*Mass and charge both decreased

33
Q

What happens to C14 when it experiences beta decay?

A

*Mass remains but charge increased

34
Q

What would be the nuclear equation for the decay of

Uranium-238?

A
35
Q

What happens to the mass or charge of a nucleus when it experiences gamma emission?

A

The mass and charge remain the same

36
Q

How can the process of radioactivity be described?

A

Random

37
Q

What happens to the radioactivity of a source over time?

A

It decreases

38
Q

What is half-life?

A

The time taken for the number of nuclei of a radioactive isotope to halve (or the count rate to halve)

39
Q

What is the half-life of the following sample?

A

2 days

40
Q

What does a short half-life mean?

A

The activity falls quickly due to rapid decay?

41
Q

What does a long half-life mean?

A

The activity falls slowly due to slow decay?

42
Q

What is radioactive contamination?

A

The unwanted presence of materials containing radioactive atoms on other materials

43
Q

What is the hazard of radioactive contamination?

A

The hazard is due to the decay of the contaminating atoms

44
Q

What is irradiation?

A

Exposing an object to nuclear radiation (the object itself does not become radioactive)

45
Q

Why is radioactive contamination so dangerous?

A

Radioactive particles could get inside the body

46
Q

Outside of the body what radioactive sources are most dangerous?

A

Beta and Gamma

47
Q

Inside the body what radioactive source is most dangerous?

A

Alpha

48
Q

What precautions should be taken around hazardous radioactive materials?

A
  • Wearing gloves / using tongs
  • Protective suits
  • Breathing apparatus
  • Limiting exposure time

Master Combined Science - Physics (Foundation) (7 decks)

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