P7 atom structure / radioactivity (paper 1) Flashcards
what three things make up a particle
- electron
- proton
- neutron
state the charges of the three things that make up a particle
- electron = 1-
- proton = 1+
- neutron = 0
what are the masses of the three things that make up a particle
- electron = 0.0005
- proton = 1
- neutron = 1
what does this diagram show
the plum pudding
what are the feature of the plum pudding
- 3D sphere
- made up of thinly spread positive charge
- small points of negative charge throughout the positive
what are the features of the nuclear model of the atom
- mostly made up of empty space
- all positive charge is concerntrated in the nucleus
- negative charges are tiny electrons orbiting the nucleus
what is the more modern atom model: plum pudding, nuclear model
the nuclear model
what are the three different types of radiation
- alpha
- beta
- gamma
what is an alpha particle
- 2 neutrons
- 2 protons
(a helium nucleus)
what is the charge of a alpha particle
2+
what is the ionisation like of an alpha particle
most ionising
describe the penetration of an alpha particle
very poor - stopped by paper
what is the range of an alpha particle like
1cm in air
what is a beta particle
a fast electron
what is the charge of a beta particle
-1
what is the ionisation like of a beta particle
moderatley ionising
describe the penetration of beta particle
moderately - stopped by thin aluminium
what is the range of a beta particle
1m
what is a gamma particle
electromagnetic waves
what is the charge of a gamma particle
0
what is the ionisation of a gamma particle like
weakly
desribe the penetration of gamma particles
highly penetrated - only stopped by dense thick lead
what is the range of gamma particles
1km
what is the mass number and proton number of a alpha particle
mass = 4
proton = 2
define decay
when a nucleus goes from an unstable state to a stable state by emitting radiation
what is the mass number and proton number of a beta particle
mass = 0
proton = -1
where are the electrons located in an atom
on shells orbitting the nucleus
what is the radius of an atom
10^-10 m
what do like charges do
repel
what do opposite charges do
attract
define half life
the time it take the number of radioactive nuclei in a smaple to decrease by 50%
how does the half life vary between isotopes and why
massively due to thhe instability of the nucleus
if the half life of a element is short what is the activity like
large activity (unstable)
if the half life of a element is long what is the activity like
little activity (stable)
what are the uses for alpha radiation
smoke detectors
what are the uses of gamma radiation
- tracers (diagnosing cancer)
- sterlising (kills bacteria)
- treating cancer (kills cells)
what are the uses of beta radiation
- measuring the thickness of paper
- tracers
why is it favoured for the half life of radioactive equipment to be long
so it doesn’t need replaceing as often
[tracers need short halflife = doesnt cause prolonged damage inside someone]
what safety action can someone they handle radioactive materials often
- move far away from it when it is in use
- wear a lead apron
what is the definition of an isotope
an atom of the same element with the same number of protons but a different number of neutrons
when does neutron emission occur
when an alpha particle collides with a nucleus
define ionisation
when an atom turns into an ion by an electron being removed
define irradiation
when something is exposed to ionising radiation, but do not become radioactive
define contaminated
the unwanted presence of a radioactive substances
What is nuclear fission
Nuclear fission is the splitting of a heavy nucleus into smaller nuclei, initiated by neutron absorption, releasing energy and additional neutrons, which can cause a chain reaction.
who discovered the plum pudding model with the beam of particles (electrons exist)
J.J thompson
what is the set up for the alpha scattering experiment
- firing alpha particles into gold foil
who first identified the concept of atoms (they cannot be divided)
- democritus - greek philosopher - and John Dalton
who found the existance of the nucleus
Rutherford (the alpha scattering experiment)
who discovered the electrons exist on shells
Bohr
who developed the idea of electrons in clouds rather than a strict orbit
Erwin Shrodinger
whoe showed the existance of neutrons
James Chadwick
State the three main outcomes from the alpha scattering experiments
- most particles passed through the gold foil = atoms are mostly empty space
- some were deflected at small angles = positve centre of atom
- very small number were deflected at large angles = small and dense
what are the units of the rate of decay
Becquerel (Bq)
define background radiation
background radiation refers to the low-level ionising radiation that is always present in the environment. This radiation comes from a variety of natural and man-made sources
what are the man-made sources of background radiation
- Medical procedures
- Nuclear power plants
- Fallout from nuclear tests
what are the risks of using radiation
- lead to tissue damage via ionisation
- increases risk of cancer
- high doses cause radiation sickness
what are the natural sources of background radiation
- Cosmic rays
- Radioactive materials in the ground
- Food and drink
what units is background radiation measured in
Sieverts (Sv)
explain the energy release involved in nuclear fission
as the nucleus splits into two smaller nuclei, lots of energy is released because the ‘products’ have less mass than the reactants
what makes nuclear fission a chain reaction
as one neutron hits a uranium atom, at least 3 more neutrons are released
what is used in nuclear power stations to control the chain reactions
a control rod moves up and down, absorbing neutrons, lower the rods are the more neutrons absorbed and slower the reaction
what is nuclear fusion
when two small nuclei collide and fuse together to form a large nucleus
explain the energy release in nuclear fusion
- when the larger nucleus is formed energy is released in the process
- the colliding nuclei need enough kinetic energy to fuse
- they release a lot of energy after that
why do the small nuclei in nuclear fusion need enough kinetic energy to fuse
because otherwise they will repel each other and not fuse because theyre both 2 positive charges
explain how nuclear fusion occurs
- gas in fusion reactor is heated by an electrical current
- gas becomes so hot it forms a plasma of small nuclei
- plasma is contained using a magnetic field to prevent it touching the container walls
- hydrogen nuclei fuse to form helium nucleus
how is the plasma in the fusion reactor contained
using a magnetic field around it because the plasma is positive and the electricity is negative
how does a moderator work in nuclear fission
it slows down the neutrons to increase reaction speed - fast neutrons won’t be absorbed
