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Yr 10-11 Physics > unit 5 > Flashcards

unit 5 Flashcards

1
Q

the structure of an atom

A

a positively charged nucleus with negatively charged electrons around it

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2
Q

how does the scattering of alpha particles by a sheet of thin metal of the atom prove the nuclear model of atom

A

the majority of them go straight through because the atom is mainly empty space

some are deflected through small angles because positive alpha particles are repelled by positive nucleus which contains most of the mass

a very small number of atoms are deflected straight back because the nucleus is extremely small

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3
Q

how can positive ions be formed

A

when atoms lose electrons

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4
Q

how can negative ions be formed

A

when atoms gain electrons

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5
Q

what is an ion

A

an electrically charged atom formed by the loss or gain of electrons

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6
Q

why do atoms gain or lose electrons

A

to become more stable

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7
Q

how to know whether an atom is stable

A

there is the same number of protons and electrons

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8
Q

how to know whether the ion is postive

A

more protons than electrons

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9
Q

how to know whether the ion is negative

A

more electrons than protons

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10
Q

what is the proton number

A

also know as atomic number
the number of protons in an atom

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11
Q

what is the nucleon number

A

also known as the mass number
the total number of particles in the nucleus of the atom

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12
Q

how can the number of neutrons be found

A

nucleon number - proton number -

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13
Q

what is the charge of a proton

A

+1

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14
Q

what is the charge of a neutron

A

0

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15
Q

what is the charge of an electron

A

-1

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16
Q

what are isotopoes

A

they are atoms of the same element that have an equal number of protons but a different number of neutrons
they tend to be more unstable due to the imbalance and are more likely to decay

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17
Q

can elements have more than 1 isotope

A

yes

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18
Q

what is nuclear fission

A

the splitting of a large, unstable nucleus into two smaller nuclei

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19
Q

what happens during fission

A

the nucleus splits into two smaller nuclei as well as two or 3 neutrons
gamma rays are also emitted
the energy stored within the nucleus of atom

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20
Q

what is the energy transfer in fission

A

energy transferred from nuclear potential to kinetic

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21
Q

why does the mass change during fission

A

the mass of the products is less than the mass of the original nucleus
this is because the remaining mass has been converted into energy which is released during the fission process

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22
Q

what is nuclear fusion

A

when two light nuclei join to form a heavier nucleus

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23
Q

what is the problem with trying to replicate nuclear fusion

A

it requires extremely high temperatures to maintain

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24
Q

where does the energy for nuclear fusion come from

A

the energy produced comes from a very small amount of the particles mass being converted into energy

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25
Q

what is background radiation

A

the radiation that exists around us all the time

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26
Q

what are the sources that contribute to background radiation

A

radon gas(in the air)
rocks and buildings
food and drink
cosmic rays

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27
Q

how can ionising nuclear radiation be measured

A

using a detector connected to a counter

28
Q

what is count rate

A

the count rate is the number of decays per second
measured in count/s or count/min

29
Q

the happens when the source is further away from the detector

A

the count rate decreases because the radiation becomes more spread out the further away it is

30
Q

what is a corrected count rate

A

count rate - background radiation

31
Q

describe the emission of radiation from a nucleus

A

spontaneous and random in direction

32
Q

when do nuclei emit radiation

A

when they need to become more stable.
it reduces the overall energy of the nucleus

33
Q

what is the process of emitting radiation known as

A

radioactive decay

34
Q

because radioactive decay is a random process, it means that:

A

equal probability of any nucleus decaying
rate of decay is unaffected by surrounding conditions
it is only possible to estimate the probability of a nuclei decaying in a given time period

35
Q

what are the different types of radioactive decay

A

alpha particles
beta particles
gamma radiation

36
Q

what does an alpha particle consist of

A

2 neutrons and 2 protons
same as a helium nucleus

37
Q

what is the charge of an alpha particle

A

+2

38
Q

what are beta particles

A

they are fast moving electrons
have a charge of -1

39
Q

what are gamma rays

A

they are electromagnetic waves and have the highest energy
they have no charge

40
Q

what is the penetrating power of alpha particles

A

stopped by paper

41
Q

what is the penetrating power of beta particles

A

stopped by a few mm of aluminum
passes through paper

42
Q

what is the penetrating power of gamma rays

A

very high, can only be stopped by lead

43
Q

what is ionisation

A

the process of which an atom becomes negative or positive by gaining or losing electrons
all nuclear radiation is capable of ionising atoms

44
Q

what happens when an atom is ionised

A

the number of electrons is has changes

45
Q

how ionising are alpha particles

A

they are the most ionising form of radiation because they leave a dense trail of ions behind them, affecting all atoms

46
Q

how ionising are beta particles

A

they are moderately ionising
leave a less dense trail then alpha but are usually more dangerous

47
Q

how ionising are gamma rays

A

least ionising form of radiation
but still can be dangerous

48
Q

what factors does the ionising effect depend on

A

the greater the charge of the radiation, the more ionising it is
the higher the kinetic energy of the radiation, the more ionising it is (alpha is highest because highest mass)

49
Q

what are the ranges of the types of radiation from shortest to longest

A

alpha (shortest)
beta
gamma rays (infinite)

50
Q

when are particles deflected in an electrical field

A

if it has charge

51
Q

when are particles deflected in a magnetic field

A

if it has charge and is moving perpendicular to it

52
Q

what particles are deflected by electric and magnetic fields

A

alpha and beta
gamma has no charge so no deflection

53
Q

in an electric field, which way are alpha particles deflected towards

A

towards the negative plate

54
Q

in an electric field, which way are beta particles deflected towards

A

the positive plate

55
Q

how does gamma radiation move in an electric field

A

not deflected so passes straight through between the plates

56
Q

what happens during alpha or beta particle decay

A

the nucleus changes to that of a different element

57
Q

why may isotopes be radioactive

A

because there is an excess of neutrons or the nucleus is too heavy

58
Q

what is half life

A

the time taken for half the nuclei of that isotope in any sample to decay

59
Q

how is radiation useful in smoke detectors

A

the alpha radiation will ionise the air within the detector, creating a current
when theres smoke, the alpha emitter is blocked
the alarm is triggered due to no current

60
Q

how can radiation be used to measure the thickness of materials

A

beta particles are used and depending on the thickness, the amount of particles being absorbed will be more or less.
this can be used to regulate the thickness of materials

61
Q

how are gamma rays used in the diagnosis and treatment of cancer

A

gamma rays penetrate the body and kill the bacteria or cancer cells

62
Q

how can radiation be used to sterilise food and medical equipment

A

gamma rays are used because objects can be sterilized without the packaging being removed
it kills any microorganisms

63
Q

what are the effects of ionising nuclear radiations on living things

A

cell death
mutations
cancer

64
Q

how are radioactive sources stored safely

A

storing them in lead lined boxes and keeping distance
minimising the amount of time the source is handled

65
Q

how is radioactive waste disposed of

A

by burying them underground to prevent it from being released into the environment

Yr 10-11 Physics (7 decks)

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