Particles Flashcards
What is an atom?
An electrically neutral collection of electrons, protons and neutrons. The number of electrons in an atom is equal to the number of protons.
What is an element?
A substance that cannot be broken down by chemical means into simpler substances
What is a nucleon?
A particle that makes up the nucleus - either a proton or neutron
What is the nucleon number?
The total number of nucleons in the nucleus(protons + neutrons). Sometimes known as the mass number
What is an ion?
An atom that has gained or lost one or more outer electrons leaving its charge unbalanced. They are charged either negatively or positively.
What is a nuclide?
A nuclide is the nucleus of a unique atom that is one with a specific number of protons and neutrons.
What is an isotope?
Atoms of an element with different numbers of neutrons but the same number of protons. They have similar qualities to the element.
What is the proton number?
The total number of protons present in the nucleus
What is the relative charge of a proton?
+1
What is the relative charge of a neutron?
0
What is the relative charge of an electron?
-1
What is the relative mass of a proton?
1
What is the relative mass of a neutron?
1
What is the relative mass of an electron?
0.0005
Which sub-atomic particle affects the element’s reactions and chemical behaviour?
Electrons
Which sub-atomic particle affects the stability of the nucleus?
Neutrons
What is the specific charge of a particle?
Particle’s ratio of its charge to its mass
What is the equation to calculate the specific charge?
Specific charge = charge/mass
What is a fundamental particle?
A particle that can’t be broken down into anything smaller
What are the units for the specific charge?
C/kg
What is the attractive force that holds the nucleus together?
Strong nuclear force
Describe the Strong nuclear force
- It is an attractive force that is stronger than the electrostatic force
- Experiments show that it has a very short range(a few femtometers( 1fm = 1*10^-15m)) and the force quickly falls beyond this distance
- It works equally between all nucleons
- At very small separations, the force must be repulsive or it would crush the nucleus
Describe the Strong Nuclear force graph
- The force is repulsive for very small separations of nucleus
- As nucleon separation increases past 0.5fm, the force becomes attractive. It reaches a maximum attractive value and then falls rapidly towards zero after ~3fm,
- The electrostatic force extends over an infinite range
What type of emissions happen during radioactive decay?
Alpha
Beta(+ or -)
Gamma
How is an alpha particle similar to a helium nucleus?
It contains 2 protons and 2 neutrons
What happens when an alpha particle is emitted?
The proton number decreases by two, and the nucleon number decreases by 4
What is a beta emission?
A fast moving electron emitted from the nucleus
Which other particle is emitted when a beta particle is emitted?
Neutrino
It carries some energy and momentum
How were neutrinos discovered?
Scientists observed beta decay and observations showed that the energy of the particles after the beta decay was less than it was before(didn’t fit the conservation of energy principle)
What did Wolfgang Pauli suggest in 1930?
Another particle was being emitted which carried away the missing energy
the particle had to be neutral and have zero or almost zero mass, as it had never been detected
What are photons?
Packets of electromagnetic radiation
What does each particle have?
Each particle has an antiparticle with the same mass and rest energy but opposite charge
What happens when energy is converted into mass?
Equal amounts of matter and antimatter is produced
What is rest energy?
The amount of energy needed to make one of the particles and the amount of energy released if one of these particles was destroyed
What is annihilation?
This occurs when a particle and antiparticle collide producing 2 photons
What factor affects the photon energy?
Frequency
What is the equation for calculating photon energy?
E=hf or
E =hc/wavelength
What is produced by the annihilation of a particle and antiparticle?
Photons of energy
What is pair production?
This is when high energy gamma photons produce a particle and its antiparticle
What is the speed of light?
3.00*10^8 m/s
What is the antiparticle of a proton?
antiproton
What is the antiparticle of an electron?
positron
What is the antiparticle of a neutron?
antineutron
What is the antiparticle of a neutrino?
antineutrino
What is the strong nuclear force?
The force that keeps the nucleons in the nucleus together. It is both repulsive and attractive.
What are the 4 fundamental forces?
Weak force
Gravity
Strong nuclear force
Electromagnetic force
What particles are responsible for the electromagnetic force?
Virtual photons
What is a virtual photon?
The exchange particle that carries the electromagnetic force between charged paticles
Why are the photons referred to as ‘virtual’?
They can’t be seen directly
If intercepted, the force wouldn’t work
What is the electromagnetic force?
A force that affects charged particles
What is the weak force?
A force that affects all types of particles
What particles are responsible for the strong nuclear force?
Gluons
What particles are responsible for the weak nuclear force?
W+ and W- bosons
Describe B- decay
A neutron in the nucleus can turn into a proton emitting and electron and an electron antineutrino. The reaction occurs via the weak interaction and is mediated by a W- boson
Describe the B+ decay
A proton decays into a neutron emitting an electron neutrino and a positron. The reaction occurs via the weak interaction and is mediated by a W+ boson
Describe the neutrino-neutron collisions
A neutron can absorb an electron neutrino, emitting a proton and an electron. The reaction occurs via the weak interaction and is mediated by a W- boson
Describe the antineutrino-proton collisions
A proton can absorb an electron antineutrino, emitting a neutron and a positron. The reaction occurs via the weak interaction and is mediated by a W+ boson
Describe electron capture
A proton in the nucleus can absorb an atomic electron forming a neutron and an electron antineutrino. The reaction occurs via the weak interaction and is mediated by a W+ boson
Describe electron-proton collisions
An electron can collide with a proton emitting a neutron and an electron antineutrino. The reaction occurs via the weak interaction and is mediated by a W- boson
Describe electromagnetic repulsion
As two electrons get close to each other, they exchange a photon as they repel
How does the mass of the boson affect the range of the force?
The larger the mass of the boson, the shorter the range of the force
What are hadrons?
Particles that feel the strong nuclear force
Why are hadrons not fundamental?
They are made of quarks
What are the two type of hadrons?
Baryons/Antibaryons
Mesons
What is a quark?
A quark is any of the set of six elementary particles together which combine into various combinations to form baryons and mesons
What are the 6 quarks?
Up, Down
Charmed, Strange
Top, Bottom
What is the charge of the quarks: up, charm and top?
2/3
What is the charge of the quarks: down, strange and bottom?
-1/3
What type of force do hadrons decay through?
Weak nuclear force
Give examples of baryons
Protons
Neutrons
Which baryon is stable out of all baryons?
The proton
Which particle do all baryons decay to except protons?
Protons
What is the baryon number?
The number of baryons in an interaction that must be conserved
What is the baryon number for baryons and antibaryons?
Baryon = 1 Antibaryon = -1
What type of force do hadrons interact through?
All four fundamental interacts
What type of force do charged hadrons interact through?
Electromagnetic interaction
Strong Nuclear interaction
What is formed when a neutron decays?
Proton + electron + Antineutrino
What are mesons?
Hadrons that do not include protons in their decay products
Give examples of mesons
Kaons
Pions
What are mesons made up of?
1 quark
1 antiquark
Give 2 characteristics of mesons
- they are all unstable
- they have a baryon number of 0
What are pions?
they are the lightest mesons
there are 3 versions: negative, positive and neutral
What are kaons?
- they are mesons which are more unstable and heavier than pions
- they have a very short lifetime and decay into pions
Through what type of force do meson and abryons interact?
Strong nuclear force
What are leptons?
Fundamental particles that do not experience the strong nuclear force
Through what type of force do leptons interact?
Weak interaction
What are the different types of leptons?
Electrons
Muons
Tau
Neutrinos
What are muons?
Heavy electrons that are unstable and decay into electrons
Why are kaons called strange particles?
They are produced in 2s and they decay into pions
What is the source of high energy particles including pions and kaons?
Cosmic ray showers
What are the conservation laws in particles?
Charge
Baryon number
Lepton number
Strangeness
When is strangeness conserved?
It is preserved during the creation of kaons but not conserved during their decay
It is also conserved through the strong and electromagnetic interaction but not through the weak interaction
Through what type of interaction can light particles decay through?
Light particles cannot decay through the strong interaction but through the weak interaction
Why is mass not necessarily conserved when particles interact or decay?
Mass can be converted into energy and vice versa
Explain why there is a minimum photon energy for an interaction and what happens when there is slightly more energy
The photon must provide enough energy to provide for the rest mass
the extra energy will provide the particles with kinetic energy
How can you calculate the minimum photon energy needed?
hf = 2E
