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gcse mock phys > radioactivity > Flashcards

radioactivity Flashcards

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1
Q

order of scientists that discovered more about atoms

A
  1. john dalton
  2. jj thompson
  3. rutherford
  4. niels bohr
  5. james chadwick
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2
Q

what is the plum pudding model

A

designed by jj thomson
sphere of positive charge with negative electrons studded into it

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3
Q

what is the rutherford scattering

A

firing alpha particles at thin gold foil, bc the mass of atom should be spread and pass through. but they were deflected meaning most mass was centred in a nucleus with positive charge.

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4
Q

what is the nuclear model

A

positively charged nucleus in cloud of negative electrons
——>
nucleus of protons that add to overall charge of nucleus, electrons orbiting at certain energy levels

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5
Q

what did james chadwick do and why

A

discovered neutrons because there was an imbalance between atomic numbers and mass numbers

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6
Q

charges of each subatomic particle

A

proton +1
neutron 0
electron -1

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7
Q

what is the bottom number on an element

A

atomic number - number of protons

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8
Q

what is an isotope

A

atoms with same number of protons but different number of neutrons

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9
Q

what is radioactive decay

A

when unstable isotopes decay into other elements, they give out radiation as they try to become more stable

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10
Q

what is ionising radiation

A

radiation that knocks electrons off atoms, making positive ions

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11
Q

what do you say about something that can know electrons off atoms easily

A

it has a high ionising power

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12
Q

structure of alpha particle and symbol

A

helium, two protons and two neutrons

a shape

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13
Q

travel distance, ionising strength, and blocking material of alpha radiation

A

only travel a few cm in air
highly ionising
stopped by sheet of paper

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14
Q

travel distance, ionising strength, and blocking material of beta particles

A

few metres in air
moderately ionising
stopped by aluminium

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15
Q

travel distance, ionising strength, and blocking material if gamma rays

A

long distance through air
weakly ionising
stopped by lead or concrete

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16
Q

what do nuclear equations show

A

how radioactive decay changes an element

17
Q

what happens when an atom emits an alpha particle

A

charge and mass DECREASE
atomic number: -2
mass number: -4
(+ [4/2] He)

18
Q

what happens to charge and mass of an atom when beta decay occurs (in terms of subatomic particles)

A

charge INCREASES, mass STAYS SAME
atomic number: +1
(+ [0/-1] e)

19
Q

what is radioactive decay

A

when unstable nuclei decay into other elements gives out radiation as they become more stable

20
Q

what is a half life

A

the time taken for half the unstable nuclei in an isotope to decay

21
Q

how do you write 1 decay per second

A

1 becquerel / bq

22
Q

what is background radiation

A

the low level radiation that is around us all the time

23
Q

3 places that background radiation comes from

A

soil
cosmic rays
nuclear explosions

24
Q

what is irradiation

A

when something is exposed to a radioactive source

25
Q

what is contamination

A

radioactive particles getting onto objects

26
Q

which radioactive rays are most dangerous OUTSIDE BODY and why

A

beta and gamma
they penetrate body to organs

27
Q

why is alpha radiation so dangerous INSIDE BODY

A

it cannot penetrate the skin so it is stuck inside
highly ionisiny

28
Q

how can gamma sources be useful

A

medical tracers

29
Q

what is radiotherapy and what are the risks

A

directing an accurate dosage of gamma rays to kill cancer cells
normal cells can be damaged

30
Q

nuclear fission vs fusion

A

fission: splitting large unstable nuvleus
fusion: joining small nuclei

31
Q

bases of nuclear fission

A

NATAC
• neutron must be absorbed
• atom splits to form two new lighter elements of roughly same size
• two or three neutrons released in process
• absorbed by other nucleus
• chain reaction

32
Q

bases of nuclear fusion and example

A

two light nuclei collide at high speed and join to make larger heavier nucleus
hydrogen nuclei fuse to produce helium nucleus

gcse mock phys (4 decks)

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