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GCSE AQA Physics > Topic 4 - Atomic Structure > Flashcards

Topic 4 - Atomic Structure Flashcards

1
Q

What is the radius of an

atom?

A

1x10^-10m

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2
Q

How big is the nucleus compared to the atom?

A

10000x smaller

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3
Q

What is the

isotope of an element?

A

an atom with the same number of protons but a different number of neutrons

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4
Q

What is

radioactive decay?

A

an unstable isotope decaying into other elements and giving out radiation as it tries to become more stable

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5
Q

What are the

three types of radiation you need to know?

A
  • alpha
  • beta
  • gamma
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6
Q

What is

ionising radiation?

A

radiation that knocks electrons off atoms, creating positive ions

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7
Q

What is the

ionising power of a radiation source?

A

how easily it can knock electrons off atoms

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8
Q

What is

alpha radiation?

A

when an alpha particle is emitted from the nucleus

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9
Q

What does an

alpha particle

consist of?

A

two neutrons and two protons

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10
Q

What are some characteristics of

alpha radiation?

  • penetratability
  • ionisation
  • absorbance

think:

A
  • they don’t penetrate very far into materials and are stopped quickly - they can only travel a few cm in air
  • they are strongly ionising
  • they are absorbed by a sheet of paper
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11
Q

How does

alpha radiation work in smoke detectors?

A

It ionises air particles, causing a current to flow. If there is smoke in the air, it binds to the ions - meaning the current stops and the alarm sounds.

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12
Q

What does a

beta particle

consist of?

A

a fast-moving electron

these have virtually no mass and a charge of -1

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13
Q

What are some characteristics of

beta radiation?

  • penetratability
  • ionisation
  • absorbance

think:

A
  • they penetrate moderately far into materials before colliding and have a range in air of a few metres
  • they are moderately ionising
  • they are absorbed by a sheet of aluminium (around 5mm)
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14
Q

What is a use of

beta radiation?

A

testing the thickness of sheets of metal

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15
Q

What does

gamma radiation

consist of?

A

waves of electromagnetic radiation

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16
Q

What are some characteristics of

gamma radiation?

  • penetratability
  • ionisation
  • absorbance

think:

A
  • they penetrate far into materials without being stopped and will travel a long distance through air
  • this means they are weakly ionising because they tend to pass through rather than collide with atoms
  • they can be absorbed by thick sheets of lead or metres of concrete
17
Q

What does a

geiger-muller tube and counter record?

A

the number of radiation counts reaching it per second

18
Q

Define

activity.

and state what this is measured in.

A

the rate at which a source decays

becquerels, Bq - 1Bq = 1 decay per second

19
Q

Define

half-life.

A

the time taken for the number of radioactive nuclei in an isotope to halve

20
Q

What is

background radiation?

A

the low-level radiation that’s around us all the time

21
Q

Where does

background radiation

come from? (3 places)

A
  • radiactivity of naturally occuring unstable isotopes which are all around us
  • radiation from space (cosmic rays), these come mostly from the sun, the Earth’s atmosphere protects us from much of this
  • radiation due to human activity
22
Q

What is a

radiation dose?

and what is this measured in?

A

the risk of harm to body tissues due to exposure to radiation

sieverts, Sv

background radiation is small, so millsieverts are often used

23
Q

Define

irradiation.

A

exposure to radiation

24
Q

How could you

reduce the effects of irradiation?

(4 ways)

A
  • keep sources in lead-lined boxes
  • stand behind barriers
  • be in a different rom
  • use remote-controlled arms
25
Q

Define

contamination.

A

unwanted radioactive atoms geting onto or into an object

26
Q

How could you

reduce the risk of contamination?

(2 ways)

A
  • use gloves and tongs when handling sources
  • wear a protective suit to avoid breathing in particles
27
Q

Why are

beta and gamma sources the most dangerous outside the body?

A

they can penetrate the body and get to the delicate organs

alpha can’t penetrate the skin and is easily blocked by a small air gap

28
Q

Why is

alpha radiation most dangerous inside the body?

A

it does all of its damage in a very localised area

beta sources are less damaging as radiation is absorbed over a wider area and some passes out of the body altogether

gamma sources are the least dangerous as they mostly pass straight out

29
Q

What are some risks to using

radiation?

A

radiation can enter living cells and ionise atoms and molecules within them, this can lead to tissue damage

lower doses tend to cause minor damage without killing the cells, this can give rise to mutant cells which divide uncontrollably

higher doses tend to kill cells completely, causing radiation sickness (keading to vomiting, tiredness and hair loss) of a lot of cells all get blatted at once

30
Q

How does

radiotherapy work?

A

Gamma rays are directed carefully and at just the right dosage to kill the cancer cells without damaging too many normal cells.

A fair bit of damage is inevitably done to normal cells, which makes the patient feel very ill.

31
Q

What is

nuclear fission?

A

a type of nuclear reaction that is used to release energy from large unstable atoms by splitting them into smaller atoms

32
Q

How does

nuclear fission work?

(6 steps)

A
  1. The nucleys absorbs a neutron.
  2. The atom splits into two new lighter elements that are roughly the same size.
  3. Two or three neutrons are also released when an atom splits.
  4. If any of these neutrons are moving slow enough to be absorbed by another nucleus, they can cause more fission to occur.
  5. The energy not transferred to the kinetic energy stores of the particles is carried away by gamma rays.
  6. This energy can be used to heat water, making steam to turn turbines and generators.
33
Q

How is the

energy produced by fission in a nuclear reactor controlled?

A

By using control rods to change how quickly the chain reaction can occur.

These are lowered and raised inside a nuclear reactor to absorb neutrons, slow down the chain reaction and control the amount of energy released.

34
Q

How does

nuclear fusion work?

A

two light nuclei collide at high speed and join to create a larger, heavier nucleus

the heavier nucleus produced by fusion does not have as much mass as the two seperate, light nuclei did, some of the mass of the light nuclei is converted to energy and released

35
Q

What are the positives and negatives of

nuclear fusion?

(1+, 2-)

A

+fusion releases a lot of energy (more than fission for a given mass of fuel)
-scientists haven’t found a way of using fusion to generate energy for us to use
-the temperatures and pressures needed for fusion are so high that fusion reactors are really hard and expensive to buil

GCSE AQA Physics (8 decks)

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