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ATOMIC PHYSICSIB PHYSICS | UNIT 11 | ATOMIC PHYSICS
RadiationIB PHYSICS | UNIT 11 | ATOMIC PHYSICS
11.1
Standard Notation
Al2713
What do you notice about the notation written below? Can you determine what each color represents?
XAZ
Mass Number
Atomic Number
Try This
Na2311
Mass Number 23
Atomic Number 11
# of Protons 11
# of Neutrons 12
MgMass Number 25
Atomic Number 12
# of Protons 12
# of Neutrons 13
2512
Sample IB Question
A nucleus of Californium (Cf) contains 98 protons and 154 neutrons. Which of the following correctly identifies this nucleus of Californium?
25498Cf
98154Cf
98252Cf
154350Cf
Isotopes vs Nuclides
C126 C14
6
Isotopes
of Carbon
Same # of protons
Same # of neutrons
NuclideSingle atom
configuration
Fundamental Forces
B115
Remember Coulomb’s Law?
𝐹 = 𝑘𝑞1𝑞2𝑟2
Opposite charges attract
Like charges repel
Fundamental Forces
Strong Nuclear Force
Electromagnetic Force
Gravitational Force
Weak Nuclear Force
• Very short range
• Very strong
Like Velcro
Unstable Nuclei
Line of Stability
More neutrons than protons
Neutrons serve as a buffer between repelling protons
Radioactivity
Radioactivity is a process where unstable elements decay into new elements and
release energy as particles and/or waves
Alpha Decay
An unstable nucleus sheds alpha particle (helium nucleus) made from 2 protons and 2 neutrons
ZAX → 𝑍−2
A−4X + 24He
ParentNuclide
DaughterNuclide
AlphaParticle
Complete the missing notation:
92238U → Th + 2
4He90234
Alpha Decay - Predict
88222Ra → 86
218Rn + ______
84208Ra → Pb + 2
4α82204
24He
Beta-Negative Decay
In an unstable nucleus, sometimes a neutral neutron is converted into a positive proton and negative electron. When this happens, another particle called an antineutrino ( ҧ𝑣𝑒) is also formed
01n → 1
1p + −10e + ҧ𝑣𝑒
ҧ𝑣𝑒𝑛
𝑝
𝑒−
anti- Charge
= 0
Beta-Negative Decay
**The proton stays and the electron and antineutrino flies away as “radiation”
ZAX → 𝑍+1
AX + −10e + ҧ𝑣𝑒
ParentNuclide
DaughterNuclide
Electron Antineutrino
Beta-Positive Decay
In an opposite process, a positive proton can be converted into a neutral neutron and positively charged electron (known as a positron). When this happens, another particle called an neutrino (𝑣𝑒) is also formed
11p → 0
1n + +10e + 𝑣𝑒
𝑣𝑒𝑝
𝑛
𝑒+
Beta-Positive Decay
ZAX → 𝑍−1
AX + +10e + 𝑣𝑒
ParentNuclide
DaughterNuclide
Positron Neutrino
614C → ___N + −1
0e + ҧ𝑣𝑒
1223Mg → ___Na + +1
0e + 𝑣𝑒
Beta Decay - Predict
90234Th → 91
234Pa + −10e + ҧ𝑣𝑒
53131I → 54
131Xe + _____ + ҧ𝑣𝑒−10e
714
1123
Gamma Decay
90234Th∗ → 90
234Th + 00γ
After an unstable nucleus has emitted an alpha or beta particle, it can contain excess energy that is released as gamma radiation
Particle Review
Particle Name
11p Proton
01n Neutron
−10e Electron
+10e Positron
ҧ𝑣𝑒 Antineutrino
𝑣𝑒 Neutrino
24He Alpha Particle
Ionizing Radiation
𝛽
𝛾
𝛼
More mass allows particles to more efficiently transfer energy and ionize an atom
Most mass
Most ionizing
Radiation Penetration
𝛽
𝛾
𝛼5 cm of air
30 cm of air
Highly Penetrating
Radiation Deflection
𝛽𝛾
𝛼
magnetic field out of screen
-10
+2
Radiation Deflection
+
–
𝛽𝛾
𝛼
-10
+2
Summary of α, β, and γ
Property Alpha (α) Beta (β+ or β-) Gamma (γ)
Relative Charge +2 +1 or -1 0
Relative Mass 4 0.0005 0
Typical Penetration 5 cm of air 30 cm of air Highly penetrating
Nature Helium nucleus Positron or Electron Electromagnetic wave
Typical Speed 107 m s-1 2.5 × 108 m s-1 3.00 × 108 m s-1
Notation 24He or 2
4α −10e or−1
0β γ or00𝛾
Ionizing Effect Strong Weak Very Weak
Abosorbed by Paper or skin 3 mm of AluminumIntensity halved by 2
cm of Lead
The Math Always Adds Up
90234Th → 91
234Pa + −10e + ҧ𝑣𝑒
1223Mg → 11
23Na + +10e + 𝑣𝑒
92238U → 90
234Th + 24He
90234Th∗ → 90
234Th + 00γ
Remembering Alpha and Beta
ZN
Z-2N-2
Proton Number, Z
Neu
tro
n N
um
ber
, N
ZN
Z+1N-1
Proton Number, Z
Neu
tro
n N
um
ber
, Nα Decay β- Decay
Mass # Mass #
92238U → 90
234Th + 24He 90
234Th → 91234Pa + −1
0e + ҧ𝑣𝑒
-4 same
Mass #
Same
Alpha Decay
82
PbLead
83
BiBismuth
84
PoPolonium
85
AtAstatine
86
RnRadon
87
FrFrancium
88
RaRadium
89
AcActinium
90
ThThorium
91
PaProtactinium
92
UUranium
93
NpNeptunium
94
PuPlutonium
95
AmAmericium
96
CmCurium
97
BkBerkelium
98
CfCalifornium
ZN
Z-2N-2
Proton Number, Z
Neu
tro
n N
um
ber
, N
ZN
Z+1N-1
Proton Number, Z
Neu
tro
n N
um
ber
, N
88226Ra → 86
222Ra + 24He
α Decay β- Decay
Mass #
- 4
α Decay of Radium-226
Beta Decay
82
PbLead
83
BiBismuth
84
PoPolonium
85
AtAstatine
86
RnRadon
87
FrFrancium
88
RaRadium
89
AcActinium
90
ThThorium
91
PaProtactinium
92
UUranium
93
NpNeptunium
94
PuPlutonium
95
AmAmericium
96
CmCurium
97
BkBerkelium
98
CfCalifornium
ZN
Z-2N-2
Proton Number, Z
Neu
tro
n N
um
ber
, N
ZN
Z+1N-1
Proton Number, Z
Neu
tro
n N
um
ber
, N
91234Pa → 92
234Ra + −10e + ҧ𝑣𝑒
α Decay β- Decay
β- Decay of Protactinium-234
Mass #
SameMass #
- 4
Keeps right on going…92
238U
90234Th
91234Pa
92234U
90230Th
82
PbLead
83
BiBismuth
84
PoPolonium
85
AtAstatine
86
RnRadon
87
FrFrancium
88
RaRadium
89
AcActinium
90
ThThorium
91
PaProtactinium
92
UUranium
88226Ra
86222Rn
84218Po
82214Pb
83214Bi
84214Po
83210Bi
81210Ti
82210Pb
81206Ti
82206Pb
Valley of Stability
Sample IB Question
Half-LifeIB PHYSICS | UNIT 11 | ATOMIC PHYSICS
11.2
Where does Radiation Come From?
Background Radiation
Radon Gas Maps
A person would receive a dose equivalent of 1 mrem from any of the following activities:• 3 days of living in Atlanta• 2 days of living in Denver• 1 year of watching television (on average)• 1 year of wearing a watch with a luminous dial• 1 coast-to-coast airline flight• 1 year living next door to a normally operating
nuclear power plant
Is Radiation Dangerous?
Radiation Sickness – 100 rem or more
Symptoms: Nausea and vomiting
Other Radiation Effects
*Values taken from the book Energy for Future Presidents →
Likelihood of cancer increases by 1%* for every radiation dose of 25 rem
*Note: This percent likelihood is added to the 20% chance from natural causes
Radioactive Decay92
238U
90234Th
91234Pa
92234U
90230Th
82
PbLead
83
BiBismuth
84
PoPolonium
85
AtAstatine
86
RnRadon
87
FrFrancium
88
RaRadium
89
AcActinium
90
ThThorium
91
PaProtactinium
92
UUranium
88226Ra
86222Rn
84218Po
82214Pb
83214Bi
84214Po
83210Bi
81210Ti
82210Pb
81206Ti
82206Pb
Half-Life
The amount of time it takes for one half of the original sample to decay
Radioactive Nuclide Half-life
Uranium-238 4.5 × 109 years
Radium-226 1,600 years
Radon-222 3.8 days
Francium-221 4.8 minutes
Astatine-217 0.03 seconds
This can be in the scale of seconds, minutes, days or even years!
Half-Life of Dice # of Rolls # of Dice
0 120
1
2
3
4
5
6
7
8
9
10
The RulesAny dice that are rolled a
6 have decayed into a
new isotope and are
removed from the sample
Half-Life =
Half-Life Example
How many half-lives does it take for there to only be __% of the original sample remaining?
100% / 2 = 50% remains after 1 half-life
50% /2 = 25% remains after 2 half-lives
25% /2 = 12.5% remains after 3 half-lives
12.5% /2 = 6.25% remains after 4 half-lives
6.25% /2 = 3.125% remains after 5 half-lives
Half Life Problem:
How many half-lives does it take for 100 g of a radioactive sample to decay to 12.5 g?
If the half-life of the sample is 7 years, how long will this take?
The half-life of radium-226 is 1601 years. What percentage remains undecayed after 4804 years?
100 g → 50 g → 25 g → 12.5 g 3 Half-Lives1 2 3
(3 half-lives) × (7 years) = 21 years
(4804 years) × (1201 years) = 4 Half-Lives
100% → 50% → 25% → 12.5% → 6.25%1 2 3 4
Radiocarbon Dating
How old is a sample of rock that has 6.25% of its original C-14. The half-life of C-14 is 5,730 years.
100% → 50% → 25% → 12.5% → 6.25%1 2 3 4
(3 half-lives) × (5730 years) =
22,920 years
Energy and Mass DefectsIB PHYSICS | UNIT 11 | ATOMIC PHYSICS
11.3
Unified Atomic Mass Unit
When measuring and reporting the mass of individual atoms and subatomic particles, kilograms are inconveniently large…
The unified atomic mass unit is defined as one-twelfth of the mass of an isolated carbon-12 atom
1 u = 1.661 × 10-27 kg
1 mole of Carbon Atoms = 0.012 kg
0.012 kg
6.02 × 1023= 1.99 × 10−26 kg
1.99 × 10−26 kg
12=
Unified Atomic Mass Unit
Electron (me) 9.110 × 10-31 kg 0.000549 u
Proton (mp) 1.673 × 10-27 kg 1.007276 u
Neutron (mn) 1.675 × 10-27 kg 1.008665 u
Unified atomic mass unit 1.661 × 10-27 kg
This is the only time that we will ever use 7 sig figs. In this case, rounding to 1.01 u just wouldn’t cut it…
𝑝 𝑛𝑒−
IB Physics Data Booklet
Einstein’s Famous Equation
According to Albert Einstein, “mass and energy are
different manifestations of the same things”
Einstein’s Famous Equation
E = mc2
What is the energy equivalence of 1 g of matter?
Energy
[J]
Mass
[kg]Speed of Light3.00 × 108 m s-1
E = (0.001 kg)(3.00 × 108 m s-1)2 = 9 × 1013 J
IB Physics Data Booklet
E = mc2
New Unit for Energy!
What is the energy equivalence of 1 proton (1.673 × 10-27 kg)?
Electron-Volt eV𝐸𝑛𝑒𝑟𝑔𝑦 𝑖𝑛 𝑒𝑉 =
𝐸𝑛𝑒𝑟𝑔𝑦 𝑖𝑛 𝐽
1.60 × 10−191 MeV = 106 eV
𝐸 = 1.673 × 10−27 3 × 108 2 = 1.5057 × 10−10 J
1.5057 × 10−10 J
1.60 × 10−19= 941,062,500 𝑒𝑉 ≈ 𝟗𝟒𝟏𝑴𝒆𝑽
New Unit for Mass
𝐸 = 𝑚𝑐2
𝑚 =𝐸
𝑐2=𝑀𝑒𝑉
𝑐2= 𝑴𝒆𝑽 𝒄−𝟐
Unified Atomic Mass Unit
Electron rest mass (me) 9.110 × 10-31 kg 0.000549 u 0.511 MeV c-2
Proton rest mass (mp) 1.673 × 10-27 kg 1.007276 u 938 MeV c-2
Neutron rest mass (mn) 1.675 × 10-27 kg 1.008665 u 940 MeV c-2
Unified atomic mass unit 1.661 × 10-27 kg 1.000000 u 931.5 MeV c-2
1 + 1 > 2
Electron rest mass (me) 0.000549 u
Proton rest mass (mp) 1.007276 u
Neutron rest mass (mn) 1.008665 u
Unified atomic mass unit 1.000000 u
A neutral Carbon-12 atom contains:
6 protons6 neutrons6 electrons
What is the total mass in terms of u?
6 × 1.007276 u
6 × 1.008665 u
6 × 0.000549 u12.09894 u
Mass Defect
Mass sum of the Carbon-12 subatomic particles:
6 × 1.007276u + 6 × 1.008665u + 6 × 0.000549u = 12.09894u
Mass of Carbon-12 atom: 12.00000u
Mass Defect 12.09894u − 12.00000u = 𝟎. 𝟎𝟗𝟖𝟗𝟒𝐮
Where did the mass go?
Energy
Binding Energy
Binding Energy is the energy required to separate all of the nucleons
…or the energy released when a nucleus is formed from its nucleons
Mass Defect → Binding Energy
𝟎. 𝟎𝟗𝟖𝟗𝟒𝐮 = 0.09894 × 931.5 𝑀𝑒𝑉 𝑐−2 =
Unified atomic mass unit 1.661 × 10-27 kg 1.000000 u 931.5 MeV c-2
E = mc2
92.1626 𝑀𝑒𝑉 𝑐−2
= (92.1626 𝑀𝑒𝑉 𝑐−2)(𝑐2)
= 𝟗𝟐. 𝟐 𝑴𝒆𝑽
Binding Energy per Nucleon
Binding Energy for Carbon-12 = 92.2 MeV
Number of Nucleons for Carbon-12 = 12
6 protons6 neutrons6 electrons
Binding Energy per Nucleon = 92.2 𝑀𝑒𝑉
12=
7.7 𝑀𝑒𝑉 𝑝𝑒𝑟 𝑁𝑢𝑐𝑙𝑒𝑜𝑛
Mass Defect → Binding Energy
Highlight the peaks
These high points represent the most
stable nuclei
Most Stable:
Iron-56
Calculate the Binding Energy
Nuclide # of p # of n # of e Atomic Mass
Helium-4 2 2 2 4.002603u
me 0.000549u
mp 1.007276u
mn 1.008665u
1u 931.5 MeV c-2
2 × 1.007276 u
2 × 1.008665 u
2 × 0.000549 u
Mass Defect
0.030377 𝑢 ×931.5 𝑀𝑒𝑉 𝑐−2
1 𝑢= 28. 296 𝑀𝑒𝑉 𝑐−2
4.032980 𝑢 – 4.002603 𝑢 = 0.030377 𝑢
𝐸 = 𝑚𝑐2 = 28. 296 𝑀𝑒𝑉 𝑐−2 𝑐2 = 𝟐𝟖. 𝟐𝟗𝟔𝑴𝒆𝑽
Convert mass
to MeV c-2
Calculate the Binding Energy
Nuclide # of p # of n # of e Atomic Mass
Fluorine-19 9 10 9 18.998403u
me 0.000549u
mp 1.007276u
mn 1.008665u
1u 931.5 MeV c-2
9 × 1.007276 u
10 × 1.008665 u
9 × 0.000549 u
Mass Defect
0.158672 𝑢 ×931.5 𝑀𝑒𝑉 𝑐−2
1 𝑢= 147.8 𝑀𝑒𝑉 𝑐−2
19.157075 𝑢 – 18.998403 𝑢 = 0.158672 𝑢
𝐸 = 𝑚𝑐2 = 147.8 𝑀𝑒𝑉 𝑐−2 𝑐2 = 𝟏𝟒𝟕. 𝟖 𝑴𝒆𝑽
Convert mass
to MeV c-2
Calculate the Binding Energy
Nuclide # of p # of n # of e Atomic Mass
Iron-56 26 30 26 55.934936u
me 0.000549u
mp 1.007276u
mn 1.008665u
1u 931.5 MeV c-2
26 × 1.007276 u
30 × 1.008665 u
26 × 0.000549 u
Mass Defect
0.528464 𝑢 ×931.5 𝑀𝑒𝑉 𝑐−2
1 𝑢= 492.26 𝑀𝑒𝑉 𝑐−2
56.463400 𝑢 – 55.934936 𝑢 = 0.528464 𝑢
𝐸 = 𝑚𝑐2 = 492.26𝑀𝑒𝑉 𝑐−2 𝑐2 = 𝟒𝟗𝟐. 𝟐𝟔𝑴𝒆𝑽
Convert mass
to MeV c-2
Fission and FusionIB PHYSICS | UNIT 11 | ATOMIC PHYSICS
11.4
IB Physics Data Booklet
Sample IB Questions
13H3 Nucleons (3 MeV per Nucleon) × (3 Nucleons)
= 9 MeV
0.1 𝑢 ×931.5 𝑀𝑒𝑉 𝑐−2
1 𝑢= 93.15 𝑀𝑒𝑉 𝑐−2
𝐸 = 𝑚𝑐2 = 93.15 𝑀𝑒𝑉 𝑐−2 𝑐2 =
𝟗𝟑. 𝟏𝟓𝑴𝒆𝑽
Mass Defect
Calculating the Binding Energy
Nuclide # of p # of n # of e Atomic Mass
Iron-56 26 30 26 55.934936u
me 0.000549u
mp 1.007276u
mn 1.008665u
1u 931.5 MeV c-2
26 × 1.007276 u30 × 1.008665 u26 × 0.000549 u
56.463400 u – 55.934936 u = 0.528454 uMass Defect
0.528454 u ×931.5 MeV c−2
1 u= 492.26 MeV c−2
𝐸 = 𝑚𝑐2 = 492.26 MeV c−2 c2 = 𝟒𝟗𝟐. 𝟐𝟔 𝐌𝐞𝐕 Binding Energy
Calculating the Binding Energy
26 × 1.007276 u + 30 × 1.008665 u + 26 × 0.000549 u→ 55.934936 u
56.463400 u – 55.934936 u
Mass Defect
0.528454 u ×931.5 MeV c−2
1 u= 492.26 MeV c−2
𝐸 = 𝑚𝑐2 = 492.26 MeV c−2 c2 = 𝟒𝟗𝟐. 𝟐𝟔 𝐌𝐞𝐕 Binding Energy
2611p + 300
1n + 26−10e → 26
56Fe
56.463400 u→ 55.934936 u
0.528454 u
Energy Released in Decay
88226Ra → Rn +
Complete the Alpha Decay reaction for Radium-226 and calculate the energy released
Radium-226 226.0254 u
Radon-222 222.0176 u
α-particle 4.0026 uBinding Energy 4.84 MeV
Mass Defect 0.0052 u
1 u 931.5 MeV c-2
86222
24He
226.0254 u→ 222.0176 u + 4.0026 u
226.0254 u→ 226.0202 u
Mass Defect = 226.0254 u - 226.0202 u = 0.0052 u
Binding Energy = 0.0052 u × 931.5 = 4.84 MeV
Fission
Chain Reaction
Fission
01n + 92
235U → 3793Rb + 55
141Cs + 201n + 0
0γ1.675 390.173 154.248 233.927 2 × 1.675
391.848 × 10-27 kg
× 10-27 kg × 10-27 kg× 10-27 kg × 10-27 kg × 10-27 kg
391.525 × 10-27 kg>
Binding Energy 181.14 MeVMass Defect 0.19446 u
391.848 × 10-27 kg - 391.525 × 10-27 kg = 0.323 × 10-27 kg
0.323 × 10−27 𝑘𝑔 ×1 𝑢
1.661 × 10−27 𝑘𝑔= 𝟎. 𝟏𝟗𝟒𝟒𝟔 𝒖
0.19446 𝑢 × 931.5 = 𝟏𝟖𝟏. 𝟏𝟒 𝑴𝒆𝑽
Fusion
Fusion
12H + 1
2H → 23He + 0
1n
Hydrogen-2 2.0141 u
Helium-3 3.0161 u
Neutron 1.0087 u
Binding Energy 3.1671 MeVMass Defect 0.0034 u
(2.0141 u + 2.0141 u) – (3.0161 u + 1.0087 u) = 0.0034 u
0.0034 u × 931.5 = 3.1671 MeV
4.0282 u 4.0248 u
Conditions for Fusion
It’s significantly more difficult to create fusion reactions here on earth
+
+
• High Pressure
• High Temperature
Fusion as a Power Source
Fusion reactions have been successfully controlled using strong magnetic fields but the energy used to run the magnets exceeds the energy released in the reaction…
Fusion vs. Fission
Fission
Fu
sio
n
The Particle AdventureIB PHYSICS | UNIT 11 | ATOMIC PHYSICS
Adapted from www.partic leadventure.org
Lawrence Berkeley National Laboratory
11.5
The Search for the Fundamental
People have long asked:"What is the world made of?" and "What holds it together?"
Why do so many things in this world share the same characteristics?People have come to realize that the matter of the world is made from a few fundamental building blocks of nature.
The word "fundamental" is key here. By fundamental building blocks we mean objects that are simple and structureless -- not made of anything smaller.
Even in ancient times, people sought to organize the world around them into fundamental elements, such as earth, air, fire, and water.
Is the Atom Fundamental?
People soon realized that they could categorize atoms into groups that shared similar chemical properties (as in the Periodic Table of the Elements). This indicated that atoms were made up of simpler building blocks, and that it was these simpler building blocks in different combinations that determined which atoms had which chemical properties.
Moreover, experiments which "looked" into an atom using particle probes indicated that atoms had structure and were not just squishy balls. These experiments helped scientists determine that atoms have a tiny but dense, positive nucleus and a cloud of negative electrons (e-).
Is the Nucleus Fundamental?
Because it appeared small, solid, and dense, scientists originally thought that the nucleus was fundamental. Later, they discovered that it was made of protons (p+), which are positively charged, and neutrons (n), which have no charge.
Are Protons/Neutrons Fundamental?
Physicists have discovered that protons and neutrons are composed of even smaller particles called quarks.
As far as we know, quarks are like points in geometry. They're not made up of anything else.
After extensively testing this theory, scientists now suspect that quarks and the electron (and a few other things we'll see in a minute) are fundamental.
Scale of the Atom
While an atom is tiny, the nucleus is ten thousand times smaller than the atom and the quarks and electrons are at least ten thousand times smaller than that. We don't know exactly how small quarks and electrons are; they are definitely smaller than 10-18 meters, and they might literally be points, but we do not know.
It is also possible that quarks and electrons are not fundamental after all, and will turn out to be made up of other, more fundamental particles. (Oh, will this madness ever end?)
What are we looking for?
Physicists constantly look for new particles. When they find them, they categorize them and try to find patterns that tell us about how the fundamental building blocks of the universe interact.
We have now discovered about two hundred particles (most of which aren't fundamental). To keep track of all of these particles, they are named with letters from the Greek and Roman alphabets.
Of course, the names of particles are but a small part of any physical theory. You should not be discouraged if you have trouble remembering them.
Take heart: even the great Enrico Fermi once said to his student (and future Nobel Laureate) Leon Lederman, "Young man, if I could remember the names of these particles, I would have been a botanist!"
The Standard Model
Physicists have developed a theory called The Standard Model that explains what the world is and what holds it together. It is a simple and comprehensive theory that explains all the hundreds of particles and complex interactions with only:• 6 quarks.• 6 leptons. The best-known lepton is the electron. We will talk about leptons later• Force carrier particles, like the photon. We will talk about these particles later.
All the known matter particles are composites of quarks and leptons, and they interact by exchanging force carrier particles.
The Standard Model
The Standard Model is a good theory. Experiments have verified its predictions to incredible precision, and all the particles predicted by this theory have been found. But it does not explain everything. For example, gravity is not included in the Standard Model.
These slides will explore the Standard Model in greater detail and will describe the experimental techniques that gave us the data to support this theory. We will also explore the intriguing questions that lie outside our current understanding of how the universe works.
Matter and Antimatter
For every type of matter particle we've found, there also exists a corresponding antimatterparticle, or antiparticle.
Antiparticles look and behave just like their corresponding matter particles, except they have opposite charges. For instance, a proton is electrically positive whereas an antiproton is electrically negative. Gravity affects matter and antimatter the same way because gravity is not a charged property and a matter particle has the same mass as its antiparticle.When a matter particle and antimatter particle meet, they annihilate into pure energy!
What is Antimatter?
Slow down! "Antimatter?" "Pure energy?" What is this, Star Trek?The idea of antimatter is strange, made all the stranger because the universe appears to be composed entirely of matter. Antimatter seems to go against everything you know about the universe.
But you can see evidence for antimatter in this early bubble chamber photo. The magnetic field in this chamber makes negative particles curl left and positive particles curl right. Many electron-positron pairs appear as if from nowhere, but are in fact from photons, which don't leave a trail. Positrons (anti-electrons) behave just like the electrons but curl in the opposite way because they have the opposite charge. (One such electron-positron pair is highlighted.)If antimatter and matter are exactly equal but opposite, then why is there so much more matter in the universe than antimatter?
Well... we don't know. It is a question that keeps physicists up at night.(The usual symbol for an antiparticle is a bar over the corresponding particle symbol. For example, the "up quark" u has an "up antiquark" designated by , pronounced u-bar. The antiparticle of a quark is an antiquark, the antiparticle of a proton is an antiproton, and so on. The antielectron is called a positron and is designated e+.)
QuarksQuarks are one type of matter particle. Most of the matter we see around us is made from protons and neutrons, which are composed of quarks.
There are six quarks, but physicists usually talk about them in terms of three pairs: up/down, charm/strange, and top/bottom. (Also, for each of these quarks, there is a corresponding antiquark.) Be glad that quarks have such silly names -- it makes them easier to remember!
Quarks
Quarks have the unusual characteristic of having a fractional electric charge, unlike the proton and electron, which have integer charges of +1 and -1 respectively. Quarks also carry another type of charge called color charge, which we will discuss later.The most elusive quark, the top quark, was discovered in 1995 after its existence had been theorized for 20 years.
The Naming of Quarks
The naming of quarks began when, in 1964, Murray Gell-Mann and George Zweig suggested that hundreds of the particles known at the time could be explained as combinations of just three fundamental particles. Gell-Mann chose the name "quarks," pronounced "kworks," for these three particles, a nonsense word used by James Joyce in the novel Finnegan's Wake:"Three quarks for Muster Mark!“
In order to make their calculations work, the quarks had to be assigned fractional electrical charges of 2/3 and -1/3. Such charges had never been observed before. Quarks are never observed by themselves, and so initially these quarks were regarded as mathematical fiction. Experiments have since convinced physicists that not only do quarks exist, but there are six of them, not three.
How did quarks get their silly names?
There are six flavors of quarks. "Flavors" just means different kinds. The two lightest are called up and down.
The third quark is called strange. It was named after the "strangely" long lifetime of the K particle, the first composite particle found to contain this quark.
The fourth quark type, the charm quark, was named on a whim. It was discovered in 1974 almost simultaneously at both the Stanford Linear Accelerator Center (SLAC) and at Brookhaven National Laboratory.
The fifth and sixth quarks were sometimes called truth and beauty in the past, but even physicists thought that was too cute.
The bottom quark was first discovered at Fermi National Lab (Fermilab) in 1977, in a composite particle called Upsilon ().
The top quark was discovered last, also at Fermilab, in 1995. It is the most massive quark. It had been predicted for a long time but had never been observed successfully until then.
Leptons
The other type of matter particles are the leptons.
There are six leptons, three of which have electrical charge and three of which do not. They appear to be point-like particles without internal structure. The best known lepton is the electron (e). The other two charged leptons are the muon(μ) and the tau(τ), which are charged like electrons but have a lot more mass. The other leptons are the three types of neutrinos (v).They have no electrical charge, very little mass, and they are very hard to find.Quarks are sociable and only exist in composite particles with other quarks, whereas leptons are solitary particles. Think of the charged leptons as independent cats with associated neutrino fleas, which are very hard to see.
For each lepton there is a corresponding antimatter antilepton. Note that the anti-electron has a special name, the "positron."
Lepton Decays
The heavier leptons, the muon and the tau, are not found in ordinary matter at all. This is because when they are produced they very quickly decay, or transform, into lighter leptons. Sometimes the tau lepton will decay into a quark, an antiquark, and a tau neutrino. Electrons and the three kinds of neutrinos are stable and thus the types we commonly see around us.
When a heavy lepton decays, one of the particles it decays into is always its corresponding neutrino. The other particles could be a quark and its antiquark, or another lepton and its antineutrino.
Physicists have observed that some types of lepton decays are possible and some are not. In order to explain this, they divided the leptons into three lepton families: the electron and its neutrino, the muon and its neutrino, and the tau and its neutrino. The number of members in each family must remain constant in a decay. (A particle and an antiparticle in the same family "cancel out" to make the total of them equal zero.)
Although leptons are solitary, they are always loyal to their families!
Neutrinos
Neutrinos are, as we've said, a type of lepton. Since they have no electrical or strong charge they almost never interact with any other particles. Most neutrinos pass right through the earth without ever interacting with a single atom of it.
Neutrinos are produced in a variety of interactions, especially in particle decays. In fact, it was through a careful study of radioactive decays that physicists hypothesized the neutrino's existence.
For example: (1) In a radioactive nucleus, a neutron at rest (zero momentum) decays, releasing a proton and an electron. (2) Because of the law of conservation of momentum, the resulting products of the decay must have a total momentum
of zero, which the observed proton and electron clearly do not. (Furthermore, if there are only two decay products, they must come out back-to-back.)
(3) Therefore, we need to infer the presence of another particle with appropriate momentum to balance the event. (4) We hypothesize that an antineutrino was released; experiments have confirmed that this is indeed what happens.
Because neutrinos were produced in great abundance in the early universe and rarely interact with matter, there are a lot of them in the Universe. Their tiny mass but huge numbers may contribute to total mass of the universe and affect its expansion.
Fundamental Particles
Charge QuarksBaryon Number
23 u c t 1
3
−13 d s b 1
3
All quarks have a strangeness number of 0 except the strange quark that has a strangeness number of –1
Charge Leptons
−1 e μ τ
0 𝑣𝑒 𝑣μ 𝑣τ
All leptons have a lepton number of 1 and antileptons have a lepton number of –1
Symbol Name
u Up
d Down
c Charm
s Strange
t Top
b Bottom
Symbol Name
e Electron
μ Muon
τ Tau
𝑣𝑒 Electron Neutrino
𝑣μ Muon Neutrino
𝑣τ Tau Neutrino
Antiparticles have the opposite charge as their corresponding particle and have a bar over their symbol
Symbol Name Charge
s Strange −13
ҧ𝑠 Antistrange +13
Build your own models
(Name)Charge = #Baryon # = Lepton # =
Charge Color
23 Green
−23 Blue
13 Purple
−13 Pink
1 Yellow
−1 Gold
0 White
Create a colored circle for each of the fundamental particle and antiparticles. There should be 24 circles in total when you are done.
For each circle, choose the color based on the charge in the chart to the right and include all of the information listed on the example below
(Symbol)
Front Back
Hadrons, Baryons, Mesons, & the Standard ModelIB PHYSICS | UNIT 11 | ATOMIC PHYSICS
11.6
Fundamental Particles
Charge QuarksBaryon Number
23 u c t 1
3
−13 d s b 1
3
All quarks have a strangeness number of 0 except the strange quark that has a strangeness number of –1
Charge Leptons
−1 e μ τ
0 𝑣𝑒 𝑣μ 𝑣τ
All leptons have a lepton number of 1 and antileptons have a lepton number of –1
Symbol Name
u Up
d Down
c Charm
s Strange
t Top
b Bottom
Symbol Name
e Electron
μ Muon
τ Tau
𝑣𝑒 Electron Neutrino
𝑣μ Muon Neutrino
𝑣τ Tau Neutrino
Antiparticles have the opposite charge as their corresponding particle and have a bar over their symbol
Symbol Name Charge
s Strange −13
ҧ𝑠 Antistrange +13
IB Physics Data Booklet
Classifying Particles
Leptons Hadrons
Electrons
Muons
Tau
Neutrinos
Pion (π)
Kaon (Κ)
Others
Proton
Neutron
Others
Mesons Baryons
Fundamental ParticlesSymbol Name Charge Baryon #
u Up +23
13
d Down −13
13
c Charm +23
13
s Strange −13
13
t Top +23
13
b Bottom −13
13
Symbol Name Charge Baryon #
തu Antiup −23 −1
3
തd Antidown +13 −1
3
തc Anticharm −23 −1
3
ҧs Antistrange +13 −1
3
ҧt Antitop −23 −1
3
തb Antibottom +13
−13
Symbol Name Charge Lepton #
e Electron −1 1
μ Muon −1 1
τ Tau −1 1
𝑣𝑒 Electron Neutrino 0 1
𝑣μ Muon Neutrino 0 1
𝑣τ Tau Neutrino 0 1
Symbol Name Charge Lepton #
തe Antielectron (positron) +1 −1
തμ Antimuon +1 −1
തτ Antitau +1 −1
ҧ𝑣𝑒 Electron Antineutrino 0 −1
ҧ𝑣μ Muon Antineutrino 0 −1
ҧ𝑣τ Tau Antineutrino 0 −1
Baryons
All Baryons are formed from a combination of 3 quarks or antiquarks
Rule: Charge must be an integer value (-1, 0, or +1)
u
d
Up Quark
Charge =
Down Quark
Charge =
Proton
Neutron
u u
u
d
d d
2/3
-1/3
(uud)
(udd)
+1
0
Mesons
All Mesons are formed from a combination of a quark and antiquark
Rule: Charge must be an integer value (-1, 0, or +1)
Kaon
D-Meson
dҧs
dതu
+1
3
−1
3
−2
3
−1
3
0
-1
Quark Confinement
Quarks have never been observed on their own
dҧs
The amount of energy required to overcome the strong nuclear force holding the quarks together gets converted into mass and forms a new quark pair
d
ҧs
ҧs
d
Conservation
For an interaction to be possible, the following must stay conserved:
Baryon # Lepton # Charge Strangeness
𝑛 → 𝑝 + 𝑒− + ҧ𝑣𝑒Baryon # 1
Lepton # 0
Charge 0
1 0 0
0 1 -1
1 -1 0
This interaction is valid because all properties are conserved
Conservation
𝑛 + 𝑝 → 𝑒+ + ҧ𝑣𝑒
𝑝 + 𝑒− → 𝑛 + 𝑣𝑒1 0
0 1
+1 -1
1 0
0 1
0 0
Baryon #
Lepton #
Charge
YesValid
1 1
0 0
0 +1
0 0
-1 -1
+1 0
Baryon #
Lepton #
Charge
NoInvalid
Exchange Particles
At the fundamental level of particle physics, forces are explained in terms of the transfer of exchange particles (gauge bosons) between
the two particles experiencing the force
These interactions are not observable so we call them virtual particles
Types of Forces
Weakest Strongest
photon
Sample IB Question
Sample IB Question
The Standard ModelMost
Common
Currently
Undiscovered
Feynman Diagrams &the Higgs BosonIB PHYSICS | UNIT 11 | ATOMIC PHYSICS
11.7
IB Physics Data Booklet
The Standard Model
The Large Hadron Collider
The Large Hadron Collider
5.4 miles
The Higgs Boson
Higgs Boson
Feynman Diagrams
Useful to represent, analyze, and predict particle interactions
Feynman Diagrams | The Rules
1. You can only draw two kinds of lines
Matter Particle Force (exchange)
Particle
Feynman Diagrams | The Rules
2. You can only connect these lines if you have two lines with arrows (one pointing in, one pointing out) meeting a single wiggly line
Interaction
Feynman Diagrams | What’s Wrong?
What’s wrong with these vertices?
No straight
lines
Both arrows
point intovertex
2 squiggles
at vertex
Arrow Direction
Left-pointing
means
antiparticle
Right-pointing
means
particle
Representing Time
The x-axis on a Feynman Diagram represents time and is read from left to right. Everything left of the vertex is the “before” condition.
e+
e-
ɣ
before after
Match these!
a photon spontaneously
“pair produces” an electron and
positron
a positron absorbs a photon and keeps going
an electron emits a photon and keeps
going
an electron and positron annihilate
into a photon
Beta-Negative Decay
𝑛 → 𝑝 + 𝑒− + ҧ𝑣𝑒
Beta-Positive Decay
𝑝 → 𝑛 + 𝑒+ + 𝑣𝑒
