Module 6.4 Flashcards
Activity
The rate of decay of the radioactive nuclei in a given isotope. It is
proportional to the total number of nuclei in the sample and is measured in
Becquerels.
Alpha Particles
A type of particle consisting of two protons and two neutrons.
Alpha particles are emitted in alpha decay and are strongly ionising, but weakly
penetrating.
Alpha-Scattering
An experiment that involved firing alpha particles at a thin gold
foil and detecting their subsequent motion. It provided evidence for the currently
accepted model of the atom.
Annihilation
The process of a particle and its antiparticle colliding and being
converted into energy. The energy is released in two photons to conserve
momentum
Antiparticles
All particles have a corresponding antiparticle with the same mass
but opposite charge and conservation numbers.
Beta Particles
An electron or positron. Beta particles are emitted during beta
decay and have medium ionising and penetrating capabilities
Beta-Minus Decay
The process of a proton inside a nucleus turning into a
neutron, and emitting a beta-minus particle (an electron) and a neutrino
Beta-Plus Decay
The process of a neutron inside a nucleus turning into a
proton, and emitting a beta-plus particle (a positron) and a neutrino.
Binding Energy
The amount of energy required to split a nucleus into all its
separate constituent nucleons. It is equivalent to the mass defect
Chain Reaction
The process of the neutrons released by a fission reaction
inducing further fissile nuclei to undergo fission
Control Rods
Rods found in nuclear reactors to absorb neutrons and control the
rate of reaction. They can be raised or lowered depending on the rate required.
Decay Constant
The probability of decay in a unit time.
Einstein’s Mass-Energy Equivalence
Mass and energy are equivalent, with the
energy equivalent of a given mass being equal to the product of the mass and the
speed of light squared.
Electron
A negatively charged fundamental particle that is found in energy levels
surrounding a nucleus.
Gamma Rays
A type of radiation emitted in gamma decay. Gamma rays are
weakly ionising but very strongly penetrating.
Hadrons
A class of subatomic particle that experiences the strong nuclear
interaction.
Half-Life
The average time it takes for the number of radioactive nuclei in a
sample of an isotope to halve.
Isotopes
A form of an element with the same number of protons but different
numbers of neutrons
Leptons
A group of elementary subatomic particles, consisting of electrons,
muons and neutrinos
Mass Defect
The difference in mass between a nucleus and the sum of the
masses of its constituent nucleons.
Moderator
A material in nuclear reactors that absorbs energy from fast moving
neutrons, to slow them down to speeds that can be absorbed by fissile neutrons to
induce fission.
Neutron
A neutrally charged nucleon, found in the nucleus of an atom. Neutrons
are a form of hadron
Nuclear Fission
The splitting a nucleus, to form two smaller daughter nuclei,
neutrons and energy
Nuclear Fusion
The joining of two smaller nuclei to form a larger nucleus and to
release energy.
Nucleon Number
The sum of the number of protons and neutrons in a given
nucleus
Positron
A positively charged particle that is the antiparticle of an electron
Proton Number
The number of protons present in the nucleus of a given
element
Proton
A positively charged nucleon, found in the nucleus of an atom. Protons
are a form of hadron
Quarks
Fundamental particle that interacts with other quarks via the strong
interaction. They change flavour via the weak interaction and annihilate with
antiquarks to form photons via the electromagnetic interaction.
Radioactive Dating
The use of radioactive isotopes with known half-lives to date
objects. The isotope that is usually used is Carbon-14
Random Nature of Decay
Radioactive decay is random - you cannot predict
when a nucleus will decay or which nucleus will decay next
Strong Nuclear Force
A force that acts between nucleons in a nucleus to keep it
stable. It is attractive at distances of up to 3fm and repulsive at separations less
than 0.5fm.
How does the alpha-scattering experiment give evidence of a small, dense nucleus
A few alpha particles bounce back
This would not happen if the positive charge in the atom was distributed evenly throughout (as in the Plum Pudding Model) which suggests they must be hitting a dense positive charge. The fact it only happens to a very small number of alpha particles shows the nucleus must be small
What are the main constituents of an atom
- Proton
- Neutron
- Electron
How many times bigger is an atom than a nucleus
roughly 100,000 times
What is the letter associated with a proton number
Z
What is the letter associated with a nucleon number
A
What is a nucleon
A particle that makes up the nucleus: a protons or a neutron
What is the strong nuclear force
The force that holds the nucleus together
It must overcome the electrostatic force of repulsion between protons, but not so much as to cause the nucleus to collapse
Describe the range of the strong force
Repulsive up to 0.5fm
Attractive up to 3fm
Which has higher density: an atom or a nucleus
A nucleus is much more dense than an atom because the atom includes a lot of empty space
True of false every particle has an antiparticle
True
Give a difference and a similarity between particles and antiparticles
Similarity: Mass
Difference: Charge
What is the antiparticle of an electron
Positron
What is a hadrom
A type of particle which is affected by the strong nuclear force
What are hadrons made of
Hadrons are made up of quarks
What are the classes of hadrons
Baryon (3 quarks)
Mesons (2 quarks)
Give 2 examples of baryons
Protons and neutrons
What are the four fundamental forces
- Strong nuclear
- Weak nuclear
- Electrostatic
- Gravity
Which of the fundamental forces are hadrons subject to
- Strong nuclear
- Weak nuclear
- Electrostatic
- Gravity
(All of them however only charged hadrons will be subject to electrostatic forces)
What are leptons
Leptons are fundamental particles which are not subject to the strong nuclear force however they still interact via the weak nuclear force
What are 3 examples are leptons
- Electrons
- Muon
- Neutrino
What are the three types of quarks
Up (u)
Down (d)
Strange (s)
And their corresponding antiparticles
State the quark composition of protons and neutrons
- Proton (uud)
- Neutron (udd)
Which quark decays in beta minus decay and what does it turn into
A down quark turns into an up quark
What quantities mush be conserved during the decay of particles
Charge, mass, baryon and lepton numbers
(And energy - but you cannot show this in a symbol equation)
What are the defining features of radioactive decay
Radioactive decay is spontaneous and random - you cannot predict when an individual nucleus will decay (or which nucleus will go next)
What features of a nucleus might cause it to radioactively decay
- Too many or too few neutrons
- Too heavy overall (too many nucleons)
- Too much energy
4 types of radiation
- Alpha
- Beta plus
- Beta minus
- Gamma
Order Alpha, Gamma and Beta radiation starting with the most ionising
- Alpha
- Beta
- Gamma
What type of radiation can only be stopped by lead or concrete
Gamma
How far does a beta particle typically penetrate in air
50cm - 1m
What materials would be needed to investigate whether a radioactive source was releasing alpha, beta or gamma
Alpha - paper
Beta - roughly 5mm thick aluminum
Gamma - thick lead sheet
A particle with nucleon number, A, and atomic number, Z, undergoes alpha decay. What are the nucleon and atomic numbers of the resulting particle (In terms of A and Z)
Nucleon number = A - 4
Atomic number = Z - 2
In beta plus decay, how does the atomic number change
It decreases
What is the activity of a source
The number of radioactive decays per second (measured in Becquerels, Bq)
What isotope is commonly used to find out how old artefacts are
Carbon-14 (in radiocarbon dating)
What occurs when a particle and antiparticle meet
- Annihilation
- When a particle and its antiparticle meet, they will annihilate each other and releases two gamma rays,
- Two rays are released in order to conserve momentum
- The mass of the particles will transform into the energy equivalent
What is pair production
When a gamma ray has enough energy to produce a particle and its antiparticle
Why does beta plus decay have a very low penetration
Because it will annihilate with matter almost immediately
What is the mass defect
The difference between the total mass of all the nucleons separately compared to the mass of the nucleus
Why is there a mass defect
Because energy is released as the nucleons bind together into a nucleus
What is binding energy
The energy required to separate a nucleus into its constituent parts
What is nuclear fission
Where a unstable nucleus splits into 2 smaller nuclei. Often occurs with the larger nuclei
The binding energy per nucleon increases when fission occurs therefore the overall process releases energy
Why is it difficult to make fusion occur on earth
There is a large repulsion between the two positively charged nuclei, therefore a lot of energy is required to overcome the repulsion and fuse them together.
It is hard to get a material that can withstand the heat and be cost effective
What is the purpose of a moderator
To slow down the neutrons so they travel slow enough to be absorbed by the uranium
They do this through elastic collisions between the moderator and the nucleus
Why are control rods essential for a nuclear power station
They stop the chain reaction from being out of control.
They absorb neutrons so that only 1 of the neutrons released in each reaction can go on to be absorbed by another uranium
If not then the nuclear reactor would overheat as too many reactions would happen at once
Give an example of a material that can be used as a moderator
Water
What is a chain reaction
A chain reaction is when exactly one neutron from each decay goes on to cause another decay - so the amount of energy released is constant and does not increase or decrease
How is nuclear waste disposed of
It is first stored in cooling ponds
It will then be put in sealed steel containers and potentially stored deep underground or underwater
Give one environmental benefit and risk of nuclear power
Benefit - no release of greenhouse gas, no contribution to global warming, does not use fossil fuel
Risk - leak or escape of material can be catastrophic
