Electrons and atoms and radiation Flashcards
What is the charge of an electron?
1.6X10^-19 coulombs
What is the definition of relative atomic mass?
The ratio of the average mass of one atom of an element to one twelfth of the mass of carbon 12
Define specific charge. How do you find it?
Charge per unit mass of an object. Charge(coulombs) ÷ mass(kg)
What is the unit for specific charge?
Ckg^-1
Coulombs per kilogram.
What can the strong nuclear force do?
It can over come the repelling force of positive protons in the nucleus of an atom.
What is the force of the strong nuclear force?
0.018 N
What is the range of the strong nuclear force?
3 X 10^-15 meters
3 Femto meters.
When is the strong nuclear force repulsive?
Beneath 0.5 fm
What happens to nucleuses that are bigger than calcium ones?
The strong nuclear force can no longer reach from one side to the other. Thus neutrons have to be added at a larger rate to carry the force from one side to the other.
Explain the B- decay of a carbon atom mass 14, protons 6
It will become a nitrogen atom with a mass of 14 and 7 protons. An electron of mass 0 and charge -1 will be emitted. ( this means the charge on each side will be equal to each other)
In addition an electron anti-neutrino will be emitted. It has a charge and mass of 0, looks like a fancy V and has a bar on top.
Remember the electron comes from the nucleus, not the electron cloud.
Explain the beta+ decay of carbon with a mass of 11 six protons.
It will become a boron atom with a mass of 11 and 5 protons. There will be an electron neutrino.( a fancy V with an e next to it. No mass or charge)
There will be a positron (positive electron) with a plus charge. This is the anti particle. It has no bar as it looks odd.
Explain electron capture with a carbon atom of mass 11 and it has 6 protons
The atom and an electron are on one side with boron 11, 5 and an electron neutrino on the other side.
What is a lepton?
A fundamental particle with a lepton number of one.
What is a hadronn?
They are composed of quarks and are split into two sub groups, baryons and mesons.
They are subject to the strong and weak nuclear forces.
What is a baryon?
They have a baryon number of one and are composed of three quarks.
There always have an integer charge.
What is a meson?
There are a quark and antiquark pair.
What can a quark not do?
Exist in isolation
What type of subatomic particle is the proton?
It a baryon. It is the most stable. All baryons will eventually decay into protons.
What is the quark composition of a proton?
Up, up down. This means a total charge of +1
What is the quark composition of a neutron?
Up, down, down meaning an overall charge of 0
What type of subatomic particle is the neutron?
It is a baryon
What are the three types of quarks?
Up, down and strange
If a meson has a strange quark in it, what type of meson do you have?
A K meson
If there is no strange quark in a meson, what type of meson is it?
π Meson
How is an antiparticle different from its normal particle?
It has the same mass but has opposite quantum numbers.
What is special about a π0 meson?
It is its own anti-particle.
What is the charge of an up quark?
Plus two thirds
What is the charge of a down quark?
-1/3
Name all the leptons
Electrons, muons and the neutrino version of each. (There is also the tauon but you don’t have to know about that)
What are the quantum numbers?
Baryon number, lepton number, charge, strangeness.
How does pair production work?
A high energy (gamma) photon interacts with the nucleus to form a particle and an anti particle pair. These could be protons, muons or electrons.
What happens in pair production if there is more energy than the amount needed to make the particles?
The energy will become kinetic energy in the particles.
Name the fundamental interaction or force responsible for beta plus decay.
Weak nuclear force
What is the exchange particle for electromagnetic force?
Virtual photon
What is the exchange particle for the strong nuclear force?
The gluon
What is the exchange particle for the weak nuclear force?
The W-, (for beta minus decay)W+ (for beta plus decay) and Z0 bosons. They all have charge and mass.
What is the exchange particle for gravity?
The graviton
What is a boson?
An exchange particle.
What will a lepton not react with?
The strong nuclear force. It will only be affected by the weak nuclear force and the electromagnetic force.
What always has to be conserved?
Baryon numbers, lepton numbers ( this is also for each family of leptons) charge and strangeness( only with strong interaction)
Why is an antineutrino emitted in in beta - decay?
To keep the lepton numbers the same. On the left, the lepton number would be 0 but the electron on the right would increase the number to 1. Therefore, an antineutrino with a lepton number of -1 must be produced to keep the lepton number at 0.
This is the same for beta + decay.
What is the symbol of a muon?
μ
What is a muon?
A negatively charged particle, similar to an electron, though it has a greater mass. It is a lepton, and has a -1 charge.
What does the muon decay into?
An electron, electron antineutrino and muon neutrino
What happens when a neutron decays into a proton?
An electron and anti electron neutrino will be produced.
A down quark with the baryon will become an up quark.
It is a result of beta minus decay.
W⁻ boson used.
What are the mesons?
Pion and kaon
What is the charge of an electron neutrino?
It is neutral.
Explain why pair production cannot take place if the frequency of the photon is below a certain level.
The energy of a photon is dependent on the frequency.
The frequency must be high enough to produce enough energy.
The frequency can’t fall below the value that means there won’t be enough energy.
What must be conserved in pair production?
Charge, lepton number, baryon number or strangeness.
What is meant by electron capture?
An atomic or orbital electron in the atom reacts with a proton in the nucleus vie the weak interaction. This results in the emission of an electron neutrino and the proton becoming a neutron.
What is the exchange particle used in electron capture?
It is caused by the weak nuclear force so its the W+ boson.
What is the role of exchange particles in an interaction?
They transfer charge, energy, momentum and force.
What is the formula triangle linking MeV to joules?
Joules
MeV X 1.6X10^-13
What are all the possible particles that a gamma photon could become when interacting with the nucleus ?
The electron and positron and the proton and the antiproton.
Define isotope.
Atoms with the same number of protons but different numbers of neutrons are called isotopes.
What can affect the stability of an atom?
The greater the no. of neutrons more than compared to the no. of protons, the more unstable the nucleus.
Why must the strong nuclear force be repulsive at very short ranges?
If it wasn’t the nucleus would be compressed to a single point.
When does alpha emission happen?
Only with very big atoms with more than 82 protons.
What happens when alpha emission occurs ?
The proton number decries by 2 and the nucleon number decreases by 4.
In pair production, what are the two particles most likely to form?
The electron and positron. This is because they have the smallest mass.
What is the antiparticle of the π+ meson ?
The π- meason.
Are mesons stable?
No.
How do mesons interact with baryons?
The strong nuclear force does it.
What is quark confinement?
The fact that quarks can’t exist in isolation.
What does the weak nuclear force have a small range?
Because the W bosons have a very big mass. Thus they have a lot of energy, thus they are unstable meaning a short half life so they can’t get very far before decaying.
Which has the greater mass, the neutron or the proton?
The neutron has a very slightly greater mass.
Why is the charge to mass ratio important?
If 2 particles have the same charge to mass ratio they will be deflected by the same amount in a magnetic or electric field.
What causes a nucleus to be unstable?
Too many neutrons or protons.
What are the 3 types of radiation?
Alpha. A helium nucleus.
Beta. A high speed electron.
Gamma. Electromagnetic radiation of wavelength 10^-14
What are em waves made of?
An electric and magnetic field at 90˚ to each other.
Range of the weak nuclear force?
10^-18 m
What happens when a particle and antiparticle meet?
They annihilate each other to give energy in the form of photons.
If there is a lot of energy, things other than photons may be created.
The created particles will go in opposite directions so as to conserve momentum.
What are the only particles that feel the strong nuclear force?
The hadrons.
What forces are mesons subject to?
Strong force, weak force and when charged the electromagnetic force.
What are the possible pi mesons that can exist?
π⁺ π° and π⁻
What do mesons decay into ?
Photons or leptons.
On a Feynman digram what are the axises?
Y axis time. It goes before during after.
X axis is space.
When a neutron decays to a proton what is the boson used in the interaction
W⁻
When 2 electrons interact what is the exchange particle?
The virtual photon.
What makes strange particles different from not strange particles?
They have a longer half life than expected
They decay with the weak interaction.
What is meant by the ionisation energy?
The energy required to (completely) remove an electron from atom from the ground state/lowest energy level
Range of the weak nuclear force.
1 X 10 ⁻¹⁸ m
What is the Feynman diagram for a neutron/ neutrino interaction?
Bottom left neutron arrow up. Top left proton arrow up.
Middle W⁻
Bottom Right neutrino up Top right electron up.
What is the Feynman diagram for beta plus decay?
Bottom left: proton up
Top left: neutron up
Middle W plus
Top right : anti electron and electron neutrino both up.
What is the Feynman diagram for a proton anti neutrino interaction?
Bottom left: proton up. Top left: neutron up. Middle W⁺ boson. Bottom right electron anti neutrino up. Top right positron up.
What is the Feynman diagram for beta minus decay?
Bottom left. Neutron up.
Top left. Proton up.
Middle W⁻ boson.
Top right. Electron and electron anti neutrino both up.
What is the Feynman digram for electron capture?
Bottom left. Proton up. Top left. neutron up. Middle W⁺ boson. Bottom left electron up. Top right electron neutrino up.
What force causes all types of decay?
The weak nuclear force.
Why is the neutrino hard to find?
It has a very small mass and no charge.
When converting from joules to mev what number do you use?
1.6 X 10^-13 and carry on as normal.
When writing an equation for a nuclear reaction, what should the symbol of the electron be?
To the left of the e have a 0 on top and -1 on bottom
