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Physics > Radioactivity > Flashcards

Radioactivity Flashcards

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1
Q

What does a nucleus atom contain?

A
  • Protons and Neutrons
  • makes up Mass of the atom
  • doesn’t take up space because it’s TINY
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2
Q

Atomic number / proton number

A

number of protons in nucleus

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3
Q

Mass number

A

Total number of protons and neutrons in a nucleus

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4
Q

Electrons

A

-negative charge
-really small
-whizz around outside of atom
-paths take up a lot of space

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5
Q

Atoms are neutral so…

A

No. Protons = No. Electrons

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6
Q

Define Isotopes

A

Atoms with the same number of protons but different number of neutrons (diff mass no.)

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7
Q

Each element only has..

A

1-2 stable isotopes

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8
Q

Radioactive isotopes

A

-nucleus is unstable➡️decays and emits radiation

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9
Q

Unstable nuclei:

A

break down at Random

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10
Q

Nucleus decay

A

-Spontaneously in its own time
-unaffected by temperature/chemical bonding
-when nucleus does decay it splits out 1or more types of radiation (alpha, beta, gamma, neutrons)
-nucleus often changes to new element

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11
Q

Nuclear radiation causes ionisation by…

A

-Bashing into atoms and knocking electrons off of them
-atoms to ions➡️ionisation

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12
Q

Ionisation pattern

A

Further the radiation can penetrate before hitting an atom and getting stopped, the less damage it will do along the way = less ionising it is

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13
Q

What can be used to to detect ionising radiation

A

-Geiger-Müller detector
-photographic film

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14
Q

Alpha particles

A

-2 protons 2 neutrons
-big heavy, slow moving
-don’t penetrate far into materials
- stopped quickly

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15
Q

Why do alpha particles create lots of ions

A

Because of big size - strongly ionising - bash into a lot of atoms & knock electrons off

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16
Q

Are alpha particles positively charged or negatively

A

-Positively - deflected by electric/magnetic fields
-emitting alpha particle decreases atomic number of nucleus by 2 and mass number by 4

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17
Q

Define Beta particles

A

electron emitted from nucleus of atom when neutron turns into proton/electron

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18
Q

What happens when a beta particle is emitted

A

Number of protons in nucleus increases by 1 - atomic number increases by 1, mass number stays same

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19
Q

Beta particles moving

A

-FAST and small

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20
Q

Beta particles penetrating

A

Penetrate moderately before ionising

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21
Q

Are beta particles charged positively or negatively?

A

Negatively- deflected by electric and magnetic fields

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22
Q

Gamma rays

A

-short wave lengths
- no mass just energy
-penetrate long way into materials without being stopped
-weak ionising - pass through rather than collide

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23
Q

Do Gamma rays have charge

A

No charge, not deflected by magnetic /electric fields

24
Q

Gamma rays emissions

A

-Always happens after beta alpha decay
-no effect on atomic /mass number of isotope

25
Q

What are alpha particles blocked by

A

Paper, skin, few cm of air

26
Q

What are beta particles blocked by

A

Thin metal

27
Q

What are gamma rays blocked by

A

Thick lead, very thick concrete

28
Q

Do radioactive samples always decrease over time

A

Yes

29
Q

Do older samples have more or less radiation

A

Less because the activity of an unstable nuclei decreases

30
Q

Define half life

A

Time taken for activity to fall by half
* short half life activity falls quickly
* long half life falls more slowly

31
Q

Beta and gamma will penetrate the skin and other body tissues this makes them suitable for…

A

Medical tracers

32
Q

What can radiation treat

A

Cancer: ionising radiation can kill/damage cells, but once cancer started then ionising radiation an be used to react as well

33
Q

RADIOTHERAPY

A

-Kills cancer cells stops dividing
-high doses of gamma rays

34
Q

Gamma rays and sterilising equipment

A

Irradiation: Food and medical equipment can be irradiated with high doses of gamma rays to kill microbes without damaging food/ equipment (not high temperatures)

35
Q

Radiation used in industry for tracers and thickness gauges

A

Detects leaks in under pipes

36
Q

What is beta radiation used for

A

Thickness control

37
Q

Ionising radiation damaging cells and tissues

A

Beta and gamma penetrate the skin AND soft tissues to reach delicate organs -more HAZARDOUS

38
Q

Risks for alpha radiation

A

-Cannot penetrate skin
-do all their damage in very localised area

39
Q

How does radiation damage cells

A

Collides with molecules- more exposure more damage

40
Q

What do lower doses of radiation cause to us

A

Minor damage - can cause mutations - cells divide uncontrollably - cancer

41
Q

Objects near a radioactive source are ———— by it

A

Irradiated

42
Q

Ways to reduce risk of irradiation

A

-keep sources in lead lined boxes
-standing behind barriers
-being in different room
- remote controlled arms

43
Q

What is contamination

A

Radioactive particles getting onto objects

44
Q

What happens when atoms are contaminated

A
  • decay releases radiation which may cause harm - very dangerous if enters body
45
Q

How to prevent contamination

A

Use gloves, tongs, protective suits, masks

46
Q

Is radioactive waste easily disposed safely

A

No

47
Q

Where is low level radioactive waste from nuclear power stations and hospitals disposed

A

Clothing, syringes buried in secure landfill sites

48
Q

How do we dispose of high level radioactive waste

A

-It is really dangerous- since it stays highly radioactive for tens of thousands of years
-sealed into glass blocks then sealed in metal canisters then buried deep under ground
- geologically stable place

49
Q

What do nuclear power stations use

A

Nuclear FISSION chain reaction

50
Q

Define Nuclear Fission

A

Splitting of atoms that release energy -eg. Uranium-235

51
Q

Neutrons released by fission reactions in a nuclear reactor have a lot of energy. How are these absorbed by uranium nuclei and sustain the chain reaction?

A

Need to be slowed down by a moderator: Graphite, Water which slows down neutrons

52
Q

What limits the rate of fission

A

Control rods made of boron by absorbing excess neutrons

53
Q

High energy neutrons and gamma rays are released in fission are highly penetrating ionising radiation what absorbs the ionising radiation?

A

Shielding: thick concrete structure containing lead or other metals

54
Q

What is nuclear FUSION

A

OPPosite of nuclear FISSION: 2 nuclei collide at HIGH speed and FUSE to create a larger heavier nucleus.

55
Q

Does the heavier nucleus have more mass

A

Not as much as the 2 separate nuclei did. some lighter nuclei are converted into energy and released

56
Q

Does FUSION release a lot of energy?

A

Yes, all the energy released in stars come form fusion

57
Q

What is the big problem with fusion only happening in…

A

Really high temperatures since positively charged nuclei have to get really close to fuse so they move really FAST to overcome force from ELECTROSTATIC REPULSION

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