gcse physics > atomic structure > Flashcards

atomic structure Flashcards

history of atom, decay, half-life, fission and fusion,nuclear waste (62 cards)

Study These Flashcards
1
Q

key scientists involved in discovering atomic structure in chronological order

A
  1. democritus (c.400 BC)
  2. john dalton (1803)
  3. jj thompson (1897)
  4. ernest rutheford (1911)
  5. niels bohr (1913)
  6. james chadwick (1932)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what is an atom?

A

simplest particle of an element

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what is an isotope?

A

atoms of an element with the same number of protons but different number of neutrons

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what is an ion?

A

an atom that has lost or gained electrons so has a
-ve/+ve charge

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what did democritus discover?

A

every substance is made from small, indivisible particles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what did john dalton discover?

A

matter is made from a finite set of atoms arranged in different combinations to form elements and compounds

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what did jj thompson discover?

A

PLUM PUDDING
an atom is a sphere of +ve ‘pudding’ with ‘-ve’ plums embedded in the pudding

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what did ernest rutheford discover?

A

GOLD FOIL
- atoms are mostly empty space
- +ve charge in small dense nucleus
- -ve electrons orbit the nucleus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what did niels bohr discover?

A

elecctrons orbit the nucleus at specific distances (energy levels/ shells)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what did james chadwick discover?

A

nucleus is made up of +ve proton and neutral neutron

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what were the differences between the expected and actual results of rutheofrds gold foil experiment?

A
  • expected the alpha rays to go straight through +ve ‘pudding’
  • instead, some alpha particles were deflected and refracted by the dense +ve nucleus
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

what did rutheford’s gold foil experiment show/prove?

A
  • most alpha particles pass straight thru -> atom is mostly empty space
  • some where deflected back -> shows atom contains +ve nucleus where +ve charge and mass is concentrated
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what is an alpha ray?

A
  • 2 protons, 2 neutrons (helium nucleus)
  • fast moving (10-15% speed of light)
  • emitted from nucleus of unstable atom
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

what is a beta particle?

A
  • high speed, fast moving electron released by the nucleus (virtually no mass, -ve charge) when a neutron spontaneously changes into a proton and electron
  • moves at 70%-80% speed of light
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

what is a gamma ray?

A

electromagnetic wave (high frequency, low wave length)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what is a neutron ray?

A

neutron

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

which atoms experience alpha decay?

A
  • no stable nuclei with atomic number of less than 84
  • unstable nuclei often decay by alpha decay
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

which atoms experience beta decay?

A
  • occurs in nuclei that are neutron rich
  • in beta decay, a neutron spontaneously changes into a prton and a electron
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

what happens in gamma decay?

A

once an unstable nucleus has decayed by alpha and/or beta decay, the nucleus emits a gamma ray to become even more stable

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

what is ionisation?

A

electrons removed from atoms by radiocative emissions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

what is penetration?

A

how easily radioactive particles can pass through materials

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

uses of alpha rays

A

smoke alarms (ionises air particles causing a current to flow. smoke interrupts the current)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

uses of gamma rays

A
  • sterilizing medical instruments before use
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

uses of beta rays

A

regulating the thickness of sheets of metal

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
why do we use half-lifes?
we cannot predict the time it will take for all of the atom to decay/ which ones will decay since radioactive decay is a random process
26
what is a half-life?
the half life of a radioisotope is the average time it takes for half the nuclei present to decay/ time it takes for the activity to fall to half its initial level
27
natural sources of background radiation
- radon from the earth's mantle and rocks - rocks and building materials - cosmic rays - food and drink eg bananas
28
artificial sources of background radiation
- medical sources eg x-rays, ct scans, radiotherapy - nuclear sources eg power plants, weapons testing
29
what is contamination?
the unwanted prescence of materials containing radioactive atoms in other materials
30
properties of alpha particles
- weakly penertrating (only travel few cm in air, don't pass through paper) - highly ionising
31
properties of beta particles
- moderatly penetrating (pass through few m of air, paper, skin but can't pass through aluminium) - moderately ionising
32
properties of gamma waves
- highly penatrating (air, paper, skin, aluminium not lead) - weakly ionising (pass through rather than collide with atoms)
33
nuclear equations
- way of showing radiocative decay atom before decay->atom after decay + radiation emitted - total mass and atomic numbers must be equal on both sides
34
what does alpha decay do to particles?
- atomic number reduces by 2 - mass number reduces by 4 - charge of the nucleus decreases
35
what does beta decay do to particles?
- number of protons in nucleus increases by 1 - mass of nucleus stays the same - beta particle = 0, -1
36
what do gamma rays do to particles?
- way of getting rid of excess energy from the nucleus - no change to the atomic mass/number - sometimes also released when a nucleus decays by alpha and beta decay
37
dangers of contamination
leads to prolonged irradiation
38
how to prevent contamination:
wearing disposable clothes and gloves when dealing with radiation sources
39
what is irradiation?
- the process of exposing a material to ionising radiation - does NOT make a material radioactive
40
prevention methods for irradiation
shielding : placing an absorber or enough air (distance) between the source of ionising radiation and the material
41
what are radition doses measured in?
sieverts (Sv) and millisieverts (mSv)
42
why is it important to reduce the risk of irradation?
minimises the dose of radiation because ionising radiation can cause cancer
43
what is activity?
- the number of decays/ second - measured in becquerels (Bq)
44
what is count rate?
- number of decays detected/sec - proportional but always less than the activity because not every radioactive decay is detected - measured with a geiger counter
45
5 rules of safe handling of radioactive materials?
1. limit exposure time 2. maximise distance from source 3. store and transport in a lead container 4. handle with tongs 5. avoid contamination
46
what is fission?
- type of nuclear reaction that releases energy from large, unstable atoms to make them stable - breaks apart large nuclei into 2 lighter elements + 2/3 neutrons also released
47
what are the 2 types of fission and which is more common?
1. spontaneous fission rarely happens 2. induced fission in nuclear fission bombs and nuclear power stations
48
2 ways to release energy from nuclear reactions...
1. FISSION - split large nuclei 2. FUSION - combine small nuclei (releases more energy)
49
what is fusion?
- nuclear reaction that releases energy by colliding 2 light nuclei to make them fuse and create a larger, heavier nuclues
50
what fuel is needed for induced fission and why is this a problem?
- Uranium-235 needed - but only 1% of naturally occuring uranium is U-235 - 99% is U-238
51
what happens to produce U-235 (nucleur fuel)?
- thermal neutron is absorbed by the nuclear fuel (U-235) to form U-236 - newly formed nucleus then fissions into 2 smaller nuclei - enrichement is used to up the proportion U-235 produced from 1% to 4%
52
what happens in fission reactors to generate energy?
1. U-236 (parent nucleus) fissions to produce 2 daughter nuclei 2. during process, energy is released along with 2/3 'fast neutrons' - although some energy is released as gamma rays during fission, most energy is the kinnetic energy of the daughter nuclei
53
nuclear fission to generate energy (as a word equation)
thermal (slow) neutron + fuel (U-235) -> parent nucleus (U-236)--spontaneous fission-> 2 x daughter nuclei + 2/3 x fast neutrons
54
what are controlled chain reactions?
- only ONE neutron from each fission goes on to be absorbed by another fuel nucleus - produces steady energy (used in nuclear power stations)
55
how do controlled chain reactions work?
- neutrons are slowed down/ MODERATED (fast->theral neutron) - done by a moderator in the reactor eg H2O, CO2, Li, in which the fuel rods sit - excess neutrons are absorbed by control rods
56
how does moderation work? (snooker idea)
- size of moderator nuclei (H2O, CO2, Li) is approx. equal to size of the neutron, so they bounce off of each other instead of being rebounded, which slows it down - so fast neutron->thermal neutron
57
what is low level nuclear waste?
contaminated surfaces eg disposable clothing
58
what is medium level nuclear waste?
reactor components and effluents
59
what is high level nuclear waste?
spent fuel rods, since the majority of the daughter nuclei produced are beta emitters so highly radioactive
60
why does high level nuclear waste have to be stored for a long time?
it will remain hazardous forever so stroing reduces risk of contamination and irradiation
61
How does fusion release energy?
- Lighter nuclei fuse to form heavier nuclei - some of the mass is converted into energy of radiation
62
Why should the walls of a nuclear reacher be made from a material with a high specific heat capacity?
- a large amount of energy transferred will only cause a small temp increase in the walls - therefore the walls of the reactor should not reach melting point
gcse physics
flashcards
Decks in class (10)
# Cards
Brainscape helps you reach your goals faster, through stronger study habits.
© 2026 Bold Learning Solutions. Terms and Conditions