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gcse phys paper 1 > atomic structure > Flashcards

atomic structure Flashcards

1
Q

radius of an atom vs radius of nucleus

A

1x10^-10
1x10^-14, 10 000x smaller

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2
Q

how does energy change across energy levels

A

further from nucleus = higher energy

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3
Q

what happens to electrons when they gain or lose energy, eg absorbs EM radiation

A

they change energy levels, atom emits EM radiation, electron returns

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4
Q

what do the numbers mean on elements

A

bottom: atomic number - number of protons (and electrons)
top: mass number - total number of protons and neutrons

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5
Q

what is an isotope

A

atoms of the same element that have different numbers of electrons

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6
Q

why can number of neutrons change but not protons

A

neutrons change to form isotopes of an element
in protons change, new element is formed

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7
Q

how do atoms become negatively charged ions

A

lose electrons

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8
Q

first ideas about atoms

A

john dalton - everything made of tiny spheres that cannot be divided

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9
Q

what followed john dalton

A

jj thompson - discovered atoms contain electrons, designed plum pudding model

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10
Q

what is the plum pudding model

A

sphere of positive charge with negative electrons studded into it

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11
Q

what followed jj thompson

A

ernest rutherford
- rutherford scattering experiment
fired alpha particles at gold foil. some passed through, meaning atom is mostly empty space. some scattered or deflected, meaning mass of atom concentrated in positively charged nucleus
- created nuclear model

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12
Q

what is the nuclear model

A

mostly empty space, mass contained in the centre in a small positive nucleus, surrounded by cloud of negative electrons

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13
Q

what followed rutherford

A

niels bohr
- discovered electrons orbit nucleus at specific distances, energy levels.
- ideas agreed with other scientific experiments
- updated nuclear model to have energy levels

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14
Q

what followed bohr

A

discovery that positive charge of nucleus came from small positive particles, protons
- james chadwick discovered that nucleus also contains neutrons, with no charge

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15
Q

what is radioactive decay

A

when isotopes with unstable nuclei give out radiation to they try to become more stable

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16
Q

what is activity and how is it measured

A

rate that an unstable nucleus decays
becquerel/Bq (decay per sec)

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17
Q

how to measure activity of a radioactive source

A

geiger-muller tube: records count-rate (number of decays each second)

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18
Q

what radiation can be given out by unstable nuclei

A

alpha
beta
gamma
neutron

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19
Q

what is ionising radiation

A

when radiation collides with atoms, electrons knocked off , making positive ions

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20
Q

what do you say about something that produces a lot of ions when they collide with a material

A

it has a high ionising power

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21
Q

structure of alpha particle and symbol

A

same as helium atom - two protons and two neutrons

a shape

22
Q

structure of beta particle and symbol

A

an electron, at high speeds

B shape

23
Q

where does beta particle come from

A

form in the nucleus when a neutron changes into a proton

24
Q

structure of gamma radiation and symbol

A

wave of EM radiation from nucleus

swirly e shape

25
travel distance, ionising strength, and blocking material of alpha radiation
only travel a few cm in air highly ionising stopped by sheet of paper
26
travel distance, ionising strength, and blocking material of beta particles
few metres in air moderately ionising stopped by a few mm aluminium
27
travel distance, ionising strength, and blocking material if gamma rays
long distance through air weakly ionising stopped by several cm lead
28
what do nuclear equations show
how radioactive decay changes an element
29
nuclear equations for alpha decay
charge and mass DECREASE atomic number: -2 mass number: -4 (+ [4/2] He)
30
nuclear equation for beta decay
charge INCREASES, mass STAYS SAME atomic number: +1 mass number: no change (+ [0/-1] e)
31
nuclear equation for gamma decay
no change
32
what is a half life
time taken for number of radioactive nuclei(/count rate) of an an isotope to halve
33
what is background radiation
the low level radiation that is around us all the time
34
sources of background radiation
natural: - rock eg granite - cosmic rays - high energy particles, blocked by earths atmosphere man made: - fall out from nuclear weapon testing - accidents at nuclear power stations
35
why might people have different levels of exposure to background radioation
- location, eg granite in cornwall - occupation, eg cosmic radiation for cabin crew
36
what is radiation dose measures in
sieverts (Sv)
37
risks of ionising radiation
increases risk of cancer
38
what is irradiation with example
when something is exposed to a radioactive source, eg sterilising using gamma radiation
39
what precautions should people that work with radioactive isotopes take
- shielding: gloves cannot be penetrated by alpha radiation, lead aprons cannot be penetrated by beta and gamma, lead walls and lead-glass screens in high levels of radiation - radiation monitor: measure radiation received, to prevent people receiving too much
40
what is contamination
when unwanted radioactive isotopes get onto or into other materials
41
how dangerous is gamma radiation
not very can penetrate skin to enter body, however likely to just pass through weakly ionising, so little damage
42
how dangerous is beta radiation
relatively they can penetrate skin into body relatively ionising, can damage cells
43
how dangerous are alpha particles
very enters body via inhaling or swallowing. it cannot penetrate the skin so it is stuck inside highly ionising, damages cells
44
how were ideas on effects of radiation published
peer review - shared with scientists to be checked and accepted
45
use of gamma rays in medicine
medical tracers to test if thyroid is working properly - thyroid should absorb iodine for hormones - patient injects/drinks radioactive iodine - gamma radiation emitted and can be detected - display can show if thyroid absorbs too much/too little
46
issues of medical tracers
- must emit gamma or beta, as they can pass out of body - must not be strongly ionising to minimise cell/tissue damage - must not decay into another radioactive isotope - must have a short half-life to minimis cell/tissue damage
47
what is radiotherapy
using ionising radiation to destroy certain cancers gamma rays are directed into body to destroy tumour
48
issues of radiotherapy and alternate solution
healthy tissue may also be damaged by the radiation radioactive rods can emit radiation to destroy tumour from inside the body, so there is damage to healthy tissue
49
nuclear fission vs fusion
fission: - splitting large unstable nuclei - chain reaction - releases less energy fusion: - joining small nuclei - not a chain reaction - releases more energy
50
process of nuclear fission
NATAC * neutron absorbed * atom splits: forms two daughter nuclei of roughly same size, and releases two or three neutrons, gamma radiation, and kinetic energy * neutrons released can be absorbed by other nuclei * chain reaction
51
to what extent is nuclear fission controlled
- speed of chain reaction can be controlled to control energy released in a nuclear reactor - uncontrolled chain reactions can cause explosions in nuclear weapons
52
process of nuclear fusion and example
- two light nuclei collide at high speed to form larger heavier nucleus - not all mass is transferred to heavier nuclei; it is converted to energy and released as radiation hydrogen nuclei fuse to form helium nucleus, which is what releases energy in stars

gcse phys paper 1 (4 decks)

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