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Physics Flashcards 8) > Particles > Flashcards

Particles Flashcards

(106 cards)

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1
Q

State the three subatomic particles in an atom.

A

Protons, neutrons, electrons.

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2
Q

Describe the structure of an atom.

A

A central nucleus containing protons and neutrons, surrounded by electrons in orbitals.

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3
Q

Where is nearly all the mass of an atom concentrated?

A

In the nucleus

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4
Q

What is the relative charge and mass of a proton?

A

Charge: +1, Mass: 1

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5
Q

What is the relative charge and mass of a neutron?

A

Charge: 0, Mass: 1.

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6
Q

What is the relative charge and mass of an electron?

A

Charge: –1, Mass: 1/1836.

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7
Q

Define a neutral atom.

A

An atom with equal numbers of protons and electrons, resulting in no overall charge.

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8
Q

Explain why the nucleus is positively charged.

A

It contains protons, which are positively charged, and neutrons, which are neutral.

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9
Q

Define specific charge.

A

The ratio of charge to mass for a particle:
specificcharge = Q/m

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10
Q

What are the SI units of specific charge?

A

Coulombs per kilogram (C kg⁻¹).

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11
Q

Why does an electron have a higher specific charge than a proton?

A

Its mass is much smaller, so the charge-to-mass ratio is greater.

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12
Q

What does the top number (A) in nuclide notation represent?

A

The nucleon (or mass) number — total number of protons and neutrons.

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13
Q

What does the bottom number (Z) in nuclide notation represent?

A

The proton (or atomic) number — total number of protons.

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14
Q

Define nucleon number.

A

The total number of protons and neutrons in a nucleus.

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15
Q

Define proton number.

A

The number of protons in a nucleus; determines the element.

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16
Q

What is the AZX notation used for?

A

To represent the structure of a nucleus:
A = nucleon number, Z = proton number, X = chemical symbol.

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17
Q

Define an isotope.

A

Nuclei of the same element with the same number of protons but different numbers of neutrons.

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18
Q

Do isotopes have the same proton number?

A

Yes — same proton number (Z), different nucleon number (A).

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19
Q

Why are some isotopes unstable?

A

An imbalance between protons and neutrons leads to radioactive decay.

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20
Q

What is isotopic data?

A

The relative amounts of each isotope of an element in a sample.

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21
Q

What tool is used to determine isotopic abundance?

A

A mass spectrometer.

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22
Q

What is carbon dating?

A

A method to date artefacts by comparing the ratio of carbon-12 to carbon-14.

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23
Q

Which two isotopes are used in carbon dating?

A

Stable carbon-12 and unstable carbon-14.

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24
Q

How do you find the number of neutrons in a nucleus?

A

Neutrons = nucleon number (A) – proton number (Z).

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25
26
Why doesn't gravity hold the nucleus together?
Gravity is too weak compared to the electrostatic repulsion between protons.
27
What fundamental force holds nucleons together in the nucleus?
The stong nuclear force
28
What particles does the strong nuclear force act between?
Quarks (protons and neutrons)
29
What is the range of the strong nuclear force?
0.5 fm to 3.0 fm.
30
At what separation does the strong force become repulsive?
Below 0.5 femtometres (fm).
31
At what separation is the strong nuclear force most attractive?
Around 1.0 fm.
32
What is the separation where the net force between nucleons is zero?
About 0.5 fm (equilibrium position).
33
What type of nuclei commonly undergo alpha decay?
Large, unstable nuclei with too many nucleons.
34
What is an alpha particle made of?
2 protons and 2 neutrons (same as a helium nucleus).
35
What happens to the atomic number and mass number in alpha decay?
Atomic number decreases by 2, mass number decreases by 4.
36
What is beta-minus (β⁻) decay?
A neutron turns into a proton, emitting an electron and an anti-electron neutrino.
37
What happens to the atomic and mass numbers in beta-minus decay?
Atomic number increases by 1, mass number stays the same.
38
What is beta-plus (β⁺) decay?
A proton turns into a neutron, emitting a positron and an electron neutrino.
39
What happens to the atomic and mass numbers in beta-plus decay?
Atomic number decreases by 1, mass number stays the same.
40
What is emitted in beta-minus decay besides the beta particle?
An anti-electron neutrino.
40
What is emitted in beta-plus decay besides the positron?
An electron neutrino.
41
Why was the neutrino hypothesised?
To account for missing energy and momentum in beta decay.
42
What is the charge and mass of a neutrino?
No charge and negligible mass.
43
What kind of energy spectrum do alpha particles have?
Discrete energy levels.
44
What kind of energy spectrum do beta particles have?
Continuous energy range.
45
Why do beta particles have a continuous range of energies?
Because the energy is shared between the beta particle and the (anti)neutrino.
46
What is an antimatter particle?
A particle with the same mass as its matter counterpart but opposite charge.
47
What are the properties of antimatter particles?
- Opposite charge to their matter counterpart - Same mass - Same rest mass energy
48
Define rest mass energy.
The energy equivalent of a particle’s mass when at rest.
49
What is a photon?
A massless quantum (or packet) of electromagnetic energy.
50
State the formula linking photon energy and frequency.
E=hf
51
State the formula linking photon energy and wavelength.
E= hc/λ ​
52
What happens to photon energy when wavelength increases?
Photon energy decreases (inverse relationship).
53
Define annihilation.
When a particle and its antiparticle collide and convert their mass into two gamma photons.
54
What is the energy of each photon in annihilation?
Equal to the rest mass energy of one of the particles: 𝐸=ℎ𝑓=𝐸rest ​
54
55
56
57
58
Define pair production.
The conversion of a high-energy photon into a particle-antiparticle pair near a nucleus.
59
Why are two photons produced in annihilation?
To conserve momentum (they move in opposite directions).
59
What is the minimum energy required for pair production?
E=hf=2Erest ​
60
What are hadrons?
Subatomic particles made of quarks that feel the strong nuclear force.
61
What are the two classes of hadrons?
Baryons (3 quarks) Mesons (quark–antiquark pair)
62
Give two examples of baryons.
Protons and neutrons
63
Give two examples of mesons.
Pions and kaons
64
What is the quark composition of a baryon?
Three quarks or three anti-quarks
65
What is the quark composition of a meson?
A quark and an anti-quark.
66
Have free quarks ever been observed?
No, quarks are always found in pairs or triplets.
67
What is baryon number?
A quantum number that counts the number of baryons in a particle or interaction.
68
What is the baryon number of a baryon?
+1
69
What is the baryon number of an anti-baryon?
-1
70
What is the baryon number of particles that are not baryons?
0
71
Why must baryons be made of only quarks (not anti-quarks)?
To ensure the total baryon number is an integer
72
What would a quark + anti-quark combination baryon violate?
It would give a non-integer baryon number — not allowed for baryons.
73
Why is the proton the most stable baryon?
It is the lightest baryon, so heavier baryons decay into it.
74
Why would proton decay violate conservation laws?
It would break baryon number conservation if it decayed into non-baryons.
75
What are the three types of pions?
π⁺, π⁻, and π⁰
76
What quarks do pions contain?
Only up and down quarks → zero strangeness
77
Which force do pions mediate between baryons?
The strong nuclear force
78
Why can virtual pions exist temporarily?
They are exchange particles — virtual particles that temporarily "violate" conservation of mass/energy.
79
What’s the difference between gluons and pions?
- Gluons bind quarks (strong interaction) - Pions bind nucleons (strong nuclear force)
80
What are the three types of kaons?
K⁺, K⁻, and K⁰
81
What do kaons decay into?
pions
82
What force is responsible for kaon decay?
the weak interaction
83
Is strangeness conserved in kaon decay?
No — strangeness is not conserved in weak interactions
84
Is strangeness conserved in kaon production?
Yes — because production occurs via the strong interaction
85
Why do kaons have long lifetimes for mesons?
Because they contain a strange quark
86
What fundamental interaction do leptons not experience?
The strong nuclear force.
87
Which three interactions can leptons experience?
Weak, electromagnetic (if charged), and gravitational.
88
Compare the muon and the electron.
Both have a charge of –1e, but the muon is heavier
89
What is the definition of a lepton?
A fundamental particle not made of quarks, which does not experience the strong force.
90
What is the quark structure of a proton?
uud
91
What is the quark structure of a neutron?
udd
92
What are strange particles?
Particles that contain a strange or anti-strange quark.
93
How are strange particles produced?
Through the strong interaction.
94
How do strange particles decay?
Through the weak interaction.
95
Why are strange particles always produced in pairs?
To conserve strangeness during the strong interaction.
96
Is strangeness conserved in all interactions?
No — only conserved in strong and electromagnetic interactions, not in the weak interaction.
97
By how much can strangeness change in weak interactions?
ΔS = 0, ±1
98
What are the four fundamental interactions in nature?
- Gravity - Electromagnetism - Strong Nuclear Force - Weak Nuclear Force
99
Which fundamental force is the strongest?
The strong nuclear force.
100
Which fundamental force is the weakest?
Gravity.
101
Which types of particles are affected by each interaction?
- Gravity: Particles with mass - Electromagnetism: Particles with charge - Weak: All particles - Strong: Hadrons only
102
Why doesn't gravity play a significant role in particle interactions?
Because it's extremely weak and only affects large masses.
103
What is the exchange particle for: 1) Strong force 2) Weak force 3) Electromagnetic force 4) Gravitational force (theorised)
1) Strong: Pions (π⁺, π⁻, π⁰) 2) Weak: W⁺, W⁻, Z⁰ bosons 3) Electromagnetic: Photon (γ) 4) Gravity (theorised): Graviton

Physics Flashcards 8) (8 decks)

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