Particles Flashcards
1
Q
What is an atom?
A
An electrically neutral collection of electrons, protons and neutrons. The number of electrons in an atom is equal to the number of protons.
2
Q
What is an element?
A
A substance that cannot be broken down by chemical means into simpler substances
3
Q
What is a nucleon?
A
A particle that makes up the nucleus - either a proton or neutron
4
Q
What is the nucleon number?
A
The total number of nucleons in the nucleus(protons + neutrons). Sometimes known as the mass number
5
Q
What is an ion?
A
An atom that has gained or lost one or more outer electrons leaving its charge unbalanced. They are charged either negatively or positively.
6
Q
What is a nuclide?
A
A nuclide is the nucleus of a unique atom that is one with a specific number of protons and neutrons.
7
Q
What is an isotope?
A
Atoms of an element with different numbers of neutrons but the same number of protons. They have similar qualities to the element.
8
Q
What is the proton number?
A
The total number of protons present in the nucleus
9
Q
What is the relative charge of a proton?
A
+1
10
Q
What is the relative charge of a neutron?
A
0
11
Q
What is the relative charge of an electron?
A
-1
12
Q
What is the relative mass of a proton?
A
1
13
Q
What is the relative mass of a neutron?
A
1
14
Q
What is the relative mass of an electron?
A
0.0005
15
Q
Which sub-atomic particle affects the element’s reactions and chemical behaviour?
A
Electrons
16
Q
Which sub-atomic particle affects the stability of the nucleus?
A
Neutrons
17
Q
What is the specific charge of a particle?
A
Particle’s ratio of its charge to its mass
18
Q
What is the equation to calculate the specific charge?
A
Specific charge = charge/mass
19
Q
What is a fundamental particle?
A
A particle that can’t be broken down into anything smaller
20
Q
What are the units for the specific charge?
A
C/kg
21
Q
What is the attractive force that holds the nucleus together?
A
Strong nuclear force
22
Q
Describe the Strong nuclear force
A
- 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
23
Q
Describe the Strong Nuclear force graph
A
- 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
24
Q
What type of emissions happen during radioactive decay?
A
Alpha
Beta(+ or -)
Gamma
25
How is an alpha particle similar to a helium nucleus?
It contains 2 protons and 2 neutrons
26
What happens when an alpha particle is emitted?
The proton number decreases by two, and the nucleon number decreases by 4
27
What is a beta emission?
A fast moving electron emitted from the nucleus
28
Which other particle is emitted when a beta particle is emitted?
Neutrino
| It carries some energy and momentum
29
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)
30
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
31
What are photons?
Packets of electromagnetic radiation
32
What does each particle have?
Each particle has an antiparticle with the same mass and rest energy but opposite charge
33
What happens when energy is converted into mass?
Equal amounts of matter and antimatter is produced
34
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
35
What is annihilation?
This occurs when a particle and antiparticle collide producing 2 photons
36
What factor affects the photon energy?
Frequency
37
What is the equation for calculating photon energy?
E=hf or
| E =hc/wavelength
38
What is produced by the annihilation of a particle and antiparticle?
Photons of energy
39
What is pair production?
This is when high energy gamma photons produce a particle and its antiparticle
40
What is the speed of light?
3.00*10^8 m/s
41
What is the antiparticle of a proton?
antiproton
42
What is the antiparticle of an electron?
positron
43
What is the antiparticle of a neutron?
antineutron
44
What is the antiparticle of a neutrino?
antineutrino
45
What is the strong nuclear force?
The force that keeps the nucleons in the nucleus together. It is both repulsive and attractive.
46
What are the 4 fundamental forces?
Weak force
Gravity
Strong nuclear force
Electromagnetic force
47
What particles are responsible for the electromagnetic force?
Virtual photons
48
What is a virtual photon?
The exchange particle that carries the electromagnetic force between charged paticles
49
Why are the photons referred to as 'virtual'?
They can't be seen directly
| If intercepted, the force wouldn't work
50
What is the electromagnetic force?
A force that affects charged particles
51
What is the weak force?
A force that affects all types of particles
52
What particles are responsible for the strong nuclear force?
Gluons
53
What particles are responsible for the weak nuclear force?
W+ and W- bosons
54
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
55
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
56
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
57
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
58
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
59
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
60
Describe electromagnetic repulsion
As two electrons get close to each other, they exchange a photon as they repel
61
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
62
What are hadrons?
Particles that feel the strong nuclear force
63
Why are hadrons not fundamental?
They are made of quarks
64
What are the two type of hadrons?
Baryons/Antibaryons
| Mesons
65
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
66
What are the 6 quarks?
Up, Down
Charmed, Strange
Top, Bottom
67
What is the charge of the quarks: up, charm and top?
2/3
68
What is the charge of the quarks: down, strange and bottom?
-1/3
69
What type of force do hadrons decay through?
Weak nuclear force
70
Give examples of baryons
Protons
| Neutrons
71
Which baryon is stable out of all baryons?
The proton
72
Which particle do all baryons decay to except protons?
Protons
73
What is the baryon number?
The number of baryons in an interaction that must be conserved
74
What is the baryon number for baryons and antibaryons?
```
Baryon = 1
Antibaryon = -1
```
75
What type of force do hadrons interact through?
All four fundamental interacts
76
What type of force do charged hadrons interact through?
Electromagnetic interaction
| Strong Nuclear interaction
77
What is formed when a neutron decays?
Proton + electron + Antineutrino
78
What are mesons?
Hadrons that do not include protons in their decay products
79
Give examples of mesons
Kaons
| Pions
80
What are mesons made up of?
1 quark
| 1 antiquark
81
Give 2 characteristics of mesons
- they are all unstable
| - they have a baryon number of 0
82
What are pions?
they are the lightest mesons
| there are 3 versions: negative, positive and neutral
83
What are kaons?
- they are mesons which are more unstable and heavier than pions
- they have a very short lifetime and decay into pions
84
Through what type of force do meson and abryons interact?
Strong nuclear force
85
What are leptons?
Fundamental particles that do not experience the strong nuclear force
86
Through what type of force do leptons interact?
Weak interaction
87
What are the different types of leptons?
Electrons
Muons
Tau
Neutrinos
88
What are muons?
Heavy electrons that are unstable and decay into electrons
89
Why are kaons called strange particles?
They are produced in 2s and they decay into pions
90
What is the source of high energy particles including pions and kaons?
Cosmic ray showers
91
What are the conservation laws in particles?
Charge
Baryon number
Lepton number
Strangeness
92
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
93
Through what type of interaction can light particles decay through?
Light particles cannot decay through the strong interaction but through the weak interaction
94
Why is mass not necessarily conserved when particles interact or decay?
Mass can be converted into energy and vice versa
95
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
96
How can you calculate the minimum photon energy needed?
hf = 2E
