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Physics > Radioactivity > Flashcards

Radioactivity Flashcards

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1
Q

What size are small molecules

A

10(-10)m

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2
Q

Why are atoms neutral

A

Because they have the same number or protons and electrons and they have an equal but opposite charge

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3
Q

What do electrons do in an atom

A

The orbits the nucleus at different set distances from the nucleus

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4
Q

When do electrons change orbit

A

When there’s absorption or emission of electromagnetic radiation

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5
Q

How do atoms form positive ions

A

If an outer electron absorbs radiation with enough energy it can move so far that it leaves the atom and is now a free electron and the atom is said to have ionised and is now a positive ion - there are now more protons than electrons

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6
Q

What are alpha, beta minus, positron, gamma rays and neutron radiation emitted from and how

A

From an unstable nuclei in a random process

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7
Q

What are alpha, beta minus, positron and gamma rays all

A

Ionising radiations

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8
Q

What is background radiation

A

The low level radiation that is around us all the time

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9
Q

What is alpha radiation

A

When an alpha particle is emitted from the nucleus

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10
Q

What is a beta minus particle

A

A fast-moving electron released by the nucleus

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11
Q

What is a beta plus particle

A

A fast moving positron (the antiparticle of the electron)

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12
Q

Mass of a beta minus particle

A

No mass

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13
Q

Charge beta minus particle

A

-1

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14
Q

Mass of beta plus particle

A

0.0005(same as electron)

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15
Q

Charge of beta plus particle

A

+1

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16
Q

What is an alpha particle equivalent too

A

A helium nucleus

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17
Q

What is a beta particle

A

An electron emitted from the nucleus

18
Q

What is a gamma ray

A

An electromagnetic radiation

19
Q

Where does background radiation come from

A

Radioactivity of naturally occurring unstable isotopes (in air, some foods, building mats), radiation from space aka cosmic rays - mostly from sun, radiation due to human activity e.g. fallout from nuclear explosions or nuclear waste

20
Q

How can radioactivity be measured

A

Using a Geiger-müller tube - which clicks each time it detects radiation
Or photographic film - more radiation the films exposed to, the darker it becomes

21
Q

How ionising are alpha particles and why

A

Stonefly ionising because of their size

22
Q

How ionising are beta particles

A

Moderately ionising

23
Q

How ionising are gamma rays and why

A

Weakly ionising because they tend to pass through rather than collide with atoms

24
Q

Process of beta minus decay

A

An atom converts one of its neutrons into a protons while releasing an electron

25
Q

Process of beta plus decay

A

a proton in the parent nucleus decays into a neutron that remains in the daughter nucleus, and the nucleus emits a neutrino and a positron,

26
Q

What happens to the mass and atomic number to alpha decay

A

Mass number decreases by 4

Atomic number decreases by 2

27
Q

What happens to the mass and atomic number to beta minus decay

A

Mass number doesn’t change

Atomic number increase by 1

28
Q

What happens to the mass and atomic number to beta plus decay

A

Mass number doesn’t change

Atomic number decreases by 1

29
Q

What happens to the mass and atomic number to neutron emission

A

Mass number decreases by 1

Atomic number stays the same

30
Q

What happens to the mass and atomic number of gamma rays

A

Neither change

31
Q

What form are nuclear equations written in

A

Atoms before decay — atom after decay + radiation emitted (alpha, beta minus, beta plus, neutron emission)

32
Q

What often happens to nuclei that have undergone radioactive decay

A

The often undergo nuclear rearrangement with a loss of energy as gamma radiation

33
Q

What is activity

A

The rate at which a source decays

34
Q

How does the activity of a radioactive source decrease over a period of time

A

Each time a radioactive nucleus decays, one more radioactive nucleus disappears, as the unstable nuclei all steadily disappear, the activity as a whole will decrease

35
Q

What is half-life

A

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

36
Q

What is the unit of activity of a radioactive isotope

A

Becquerel, Bq

37
Q

What is a random process and how can we calculate it

A

Radioactive sources contain radioactive isotopes that give out radiation from the nuclei of their atoms -process=random
If there are lots of nuclei u can predict how many will have decayed in a given time using half-life

38
Q

What are the dangers of ionising radiation

A

It can enter living cells and ionise atoms and molecules within them-lead to tissue damage
Lower doses tend to cause minor damage without killing the cells, can give rise to mutant cells dividing uncontrollably-cancer
Higher doses can kill cells completely -lead to radiation sickness

39
Q

Dangers of beta and gamma radiation

A

Can penetrate the body and get into vital organs

Alpha cannot penetrate skin

40
Q

How can we prevent harm caused by ionising radiation

A

Hospitals limit staff and patient exposure to radiation e.g. shielding is used protecting staff and untreated body parts white short half-life used

41
Q

What are the differences between irradiation effects and contamination effects

A

Contamination- contaminating atoms can decay and release radiation, radioactive particles could get in your body and the person becomes contaminated

Physics (7 decks)

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