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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 Coulombโs Law?
๐น = ๐๐1๐2๐2
Opposite charges attract
Like charges repel
Fundamental Forces
Strong Nuclear Force
Electromagnetic Force
Gravitational Force
Weak Nuclear Force
โข Very short range
โข 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 โ ๐โ2
Aโ4X + 24He
ParentNuclide
DaughterNuclide
AlphaParticle
Complete the missing notation:
92238U โ Th + 2
4He90234
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 ( าง๐ฃ๐) is also formed
01n โ 1
1p + โ10e + าง๐ฃ๐
าง๐ฃ๐๐
๐
๐โ
anti- Charge
= 0
Beta-Negative Decay
**The proton stays and the electron and antineutrino flies away as โradiationโ
ZAX โ ๐+1
AX + โ10e + าง๐ฃ๐
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 (๐ฃ๐) is also formed
11p โ 0
1n + +10e + ๐ฃ๐
๐ฃ๐๐
๐
๐+
Beta-Positive Decay
ZAX โ ๐โ1
AX + +10e + ๐ฃ๐
ParentNuclide
DaughterNuclide
Positron Neutrino
614C โ ___N + โ1
0e + าง๐ฃ๐
1223Mg โ ___Na + +1
0e + ๐ฃ๐
Beta Decay - Predict
90234Th โ 91
234Pa + โ10e + าง๐ฃ๐
53131I โ 54
131Xe + _____ + าง๐ฃ๐โ10e
714
1123
Gamma Decay
90234Thโ โ 90
234Th + 00ฮณ
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
โ10e Electron
+10e Positron
าง๐ฃ๐ Antineutrino
๐ฃ๐ Neutrino
24He Alpha Particle
Ionizing Radiation
๐ฝ
๐พ
๐ผ
More mass allows particles to more efficiently transfer energy and ionize an atom
Most mass
Most ionizing
Summary of ฮฑ, ฮฒ, and ฮณ
Property Alpha (ฮฑ) Beta (ฮฒ+ or ฮฒ-) Gamma (ฮณ)
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 ร 108 m s-1 3.00 ร 108 m s-1
Notation 24He or 2
4ฮฑ โ10e orโ1
0ฮฒ ฮณ or00๐พ
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 โ 91
234Pa + โ10e + าง๐ฃ๐
1223Mg โ 11
23Na + +10e + ๐ฃ๐
92238U โ 90
234Th + 24He
90234Thโ โ 90
234Th + 00ฮณ
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
, Nฮฑ Decay ฮฒ- Decay
Mass # Mass #
92238U โ 90
234Th + 24He 90
234Th โ 91234Pa + โ1
0e + าง๐ฃ๐
-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 โ 86
222Ra + 24He
ฮฑ Decay ฮฒ- Decay
Mass #
- 4
ฮฑ 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 โ 92
234Ra + โ10e + าง๐ฃ๐
ฮฑ Decay ฮฒ- Decay
ฮฒ- Decay of Protactinium-234
Mass #
SameMass #
- 4
Keeps right on goingโฆ92
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
Background Radiation
Radon Gas Maps
A person would receive a dose equivalent of 1 mrem from any of the following activities:โข 3 days of living in Atlantaโข 2 days of living in Denverโข 1 year of watching television (on average)โข 1 year of wearing a watch with a luminous dialโข 1 coast-to-coast airline flightโข 1 year living next door to a normally operating
nuclear power plant
Is Radiation Dangerous?
Radiation Sickness โ 100 rem or more
Symptoms: Nausea and vomiting
Other Radiation Effects
*Values taken from the book Energy for Future Presidents โ
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 ร 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 โ 50 g โ 25 g โ 12.5 g 3 Half-Lives1 2 3
(3 half-lives) ร (7 years) = 21 years
(4804 years) ร (1201 years) = 4 Half-Lives
100% โ 50% โ 25% โ 12.5% โ 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% โ 50% โ 25% โ 12.5% โ 6.25%1 2 3 4
(3 half-lives) ร (5730 years) =
22,920 years
Unified Atomic Mass Unit
When measuring and reporting the mass of individual atoms and subatomic particles, kilograms are inconveniently largeโฆ
The unified atomic mass unit is defined as one-twelfth of the mass of an isolated carbon-12 atom
1 u = 1.661 ร 10-27 kg
1 mole of Carbon Atoms = 0.012 kg
0.012 kg
6.02 ร 1023= 1.99 ร 10โ26 kg
1.99 ร 10โ26 kg
12=
Unified Atomic Mass Unit
Electron (me) 9.110 ร 10-31 kg 0.000549 u
Proton (mp) 1.673 ร 10-27 kg 1.007276 u
Neutron (mn) 1.675 ร 10-27 kg 1.008665 u
Unified atomic mass unit 1.661 ร 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 wouldnโt cut itโฆ
๐ ๐๐โ
Einsteinโs Famous Equation
According to Albert Einstein, โmass and energy are
different manifestations of the same thingsโ
Einsteinโs Famous Equation
E = mc2
What is the energy equivalence of 1 g of matter?
Energy
[J]
Mass
[kg]Speed of Light3.00 ร 108 m s-1
E = (0.001 kg)(3.00 ร 108 m s-1)2 = 9 ร 1013 J
New Unit for Energy!
What is the energy equivalence of 1 proton (1.673 ร 10-27 kg)?
Electron-Volt eV๐ธ๐๐๐๐๐ฆ ๐๐ ๐๐ =
๐ธ๐๐๐๐๐ฆ ๐๐ ๐ฝ
1.60 ร 10โ191 MeV = 106 eV
๐ธ = 1.673 ร 10โ27 3 ร 108 2 = 1.5057 ร 10โ10 J
1.5057 ร 10โ10 J
1.60 ร 10โ19= 941,062,500 ๐๐ โ ๐๐๐๐ด๐๐ฝ
Unified Atomic Mass Unit
Electron rest mass (me) 9.110 ร 10-31 kg 0.000549 u 0.511 MeV c-2
Proton rest mass (mp) 1.673 ร 10-27 kg 1.007276 u 938 MeV c-2
Neutron rest mass (mn) 1.675 ร 10-27 kg 1.008665 u 940 MeV c-2
Unified atomic mass unit 1.661 ร 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 ร 1.007276 u
6 ร 1.008665 u
6 ร 0.000549 u12.09894 u
Mass Defect
Mass sum of the Carbon-12 subatomic particles:
6 ร 1.007276u + 6 ร 1.008665u + 6 ร 0.000549u = 12.09894u
Mass of Carbon-12 atom: 12.00000u
Mass Defect 12.09894u โ 12.00000u = ๐. ๐๐๐๐๐๐ฎ
Where did the mass go?
Energy
Binding Energy
Binding Energy is the energy required to separate all of the nucleons
โฆor the energy released when a nucleus is formed from its nucleons
Mass Defect โ Binding Energy
๐. ๐๐๐๐๐๐ฎ = 0.09894 ร 931.5 ๐๐๐ ๐โ2 =
Unified atomic mass unit 1.661 ร 10-27 kg 1.000000 u 931.5 MeV c-2
E = mc2
92.1626 ๐๐๐ ๐โ2
= (92.1626 ๐๐๐ ๐โ2)(๐2)
= ๐๐. ๐ ๐ด๐๐ฝ
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 = 92.2 ๐๐๐
12=
7.7 ๐๐๐ ๐๐๐ ๐๐ข๐๐๐๐๐
Mass Defect โ 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 ร 1.007276 u
2 ร 1.008665 u
2 ร 0.000549 u
Mass Defect
0.030377 ๐ข ร931.5 ๐๐๐ ๐โ2
1 ๐ข= 28. 296 ๐๐๐ ๐โ2
4.032980 ๐ข โ 4.002603 ๐ข = 0.030377 ๐ข
๐ธ = ๐๐2 = 28. 296 ๐๐๐ ๐โ2 ๐2 = ๐๐. ๐๐๐๐ด๐๐ฝ
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 ร 1.007276 u
10 ร 1.008665 u
9 ร 0.000549 u
Mass Defect
0.158672 ๐ข ร931.5 ๐๐๐ ๐โ2
1 ๐ข= 147.8 ๐๐๐ ๐โ2
19.157075 ๐ข โ 18.998403 ๐ข = 0.158672 ๐ข
๐ธ = ๐๐2 = 147.8 ๐๐๐ ๐โ2 ๐2 = ๐๐๐. ๐ ๐ด๐๐ฝ
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 ร 1.007276 u
30 ร 1.008665 u
26 ร 0.000549 u
Mass Defect
0.528464 ๐ข ร931.5 ๐๐๐ ๐โ2
1 ๐ข= 492.26 ๐๐๐ ๐โ2
56.463400 ๐ข โ 55.934936 ๐ข = 0.528464 ๐ข
๐ธ = ๐๐2 = 492.26๐๐๐ ๐โ2 ๐2 = ๐๐๐. ๐๐๐ด๐๐ฝ
Convert mass
to MeV c-2
Sample IB Questions
13H3 Nucleons (3 MeV per Nucleon) ร (3 Nucleons)
= 9 MeV
0.1 ๐ข ร931.5 ๐๐๐ ๐โ2
1 ๐ข= 93.15 ๐๐๐ ๐โ2
๐ธ = ๐๐2 = 93.15 ๐๐๐ ๐โ2 ๐2 =
๐๐. ๐๐๐ด๐๐ฝ
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 ร 1.007276 u30 ร 1.008665 u26 ร 0.000549 u
56.463400 u โ 55.934936 u = 0.528454 uMass Defect
0.528454 u ร931.5 MeV cโ2
1 u= 492.26 MeV cโ2
๐ธ = ๐๐2 = 492.26 MeV cโ2 c2 = ๐๐๐. ๐๐ ๐๐๐ Binding Energy
Calculating the Binding Energy
26 ร 1.007276 u + 30 ร 1.008665 u + 26 ร 0.000549 uโ 55.934936 u
56.463400 u โ 55.934936 u
Mass Defect
0.528454 u ร931.5 MeV cโ2
1 u= 492.26 MeV cโ2
๐ธ = ๐๐2 = 492.26 MeV cโ2 c2 = ๐๐๐. ๐๐ ๐๐๐ Binding Energy
2611p + 300
1n + 26โ10e โ 26
56Fe
56.463400 uโ 55.934936 u
0.528454 u
Energy Released in Decay
88226Ra โ Rn +
Complete the Alpha Decay reaction for Radium-226 and calculate the energy released
Radium-226 226.0254 u
Radon-222 222.0176 u
ฮฑ-particle 4.0026 uBinding Energy 4.84 MeV
Mass Defect 0.0052 u
1 u 931.5 MeV c-2
86222
24He
226.0254 uโ 222.0176 u + 4.0026 u
226.0254 uโ 226.0202 u
Mass Defect = 226.0254 u - 226.0202 u = 0.0052 u
Binding Energy = 0.0052 u ร 931.5 = 4.84 MeV
Fission
01n + 92
235U โ 3793Rb + 55
141Cs + 201n + 0
0ฮณ1.675 390.173 154.248 233.927 2 ร 1.675
391.848 ร 10-27 kg
ร 10-27 kg ร 10-27 kgร 10-27 kg ร 10-27 kg ร 10-27 kg
391.525 ร 10-27 kg>
Binding Energy 181.14 MeVMass Defect 0.19446 u
391.848 ร 10-27 kg - 391.525 ร 10-27 kg = 0.323 ร 10-27 kg
0.323 ร 10โ27 ๐๐ ร1 ๐ข
1.661 ร 10โ27 ๐๐= ๐. ๐๐๐๐๐ ๐
0.19446 ๐ข ร 931.5 = ๐๐๐. ๐๐ ๐ด๐๐ฝ
Fusion
12H + 1
2H โ 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) โ (3.0161 u + 1.0087 u) = 0.0034 u
0.0034 u ร 931.5 = 3.1671 MeV
4.0282 u 4.0248 u
Conditions for Fusion
Itโs significantly more difficult to create fusion reactions here on earth
+
+
โข High Pressure
โข 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 reactionโฆ
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:โข 6 quarks.โข 6 leptons. The best-known lepton is the electron. We will talk about leptons laterโข 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!โ
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(ฮผ) and the tau(ฯ), 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
โ13 d s b 1
3
All quarks have a strangeness number of 0 except the strange quark that has a strangeness number of โ1
Charge Leptons
โ1 e ฮผ ฯ
0 ๐ฃ๐ ๐ฃฮผ ๐ฃฯ
All leptons have a lepton number of 1 and antileptons have a lepton number of โ1
Symbol Name
u Up
d Down
c Charm
s Strange
t Top
b Bottom
Symbol Name
e Electron
ฮผ Muon
ฯ Tau
๐ฃ๐ Electron Neutrino
๐ฃฮผ Muon Neutrino
๐ฃฯ Tau Neutrino
Antiparticles have the opposite charge as their corresponding particle and have a bar over their symbol
Symbol Name Charge
s Strange โ13
าง๐ Antistrange +13
Build your own models
(Name)Charge = #Baryon # = Lepton # =
Charge Color
23 Green
โ23 Blue
13 Purple
โ13 Pink
1 Yellow
โ1 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
Fundamental Particles
Charge QuarksBaryon Number
23 u c t 1
3
โ13 d s b 1
3
All quarks have a strangeness number of 0 except the strange quark that has a strangeness number of โ1
Charge Leptons
โ1 e ฮผ ฯ
0 ๐ฃ๐ ๐ฃฮผ ๐ฃฯ
All leptons have a lepton number of 1 and antileptons have a lepton number of โ1
Symbol Name
u Up
d Down
c Charm
s Strange
t Top
b Bottom
Symbol Name
e Electron
ฮผ Muon
ฯ Tau
๐ฃ๐ Electron Neutrino
๐ฃฮผ Muon Neutrino
๐ฃฯ Tau Neutrino
Antiparticles have the opposite charge as their corresponding particle and have a bar over their symbol
Symbol Name Charge
s Strange โ13
าง๐ Antistrange +13
Classifying Particles
Leptons Hadrons
Electrons
Muons
Tau
Neutrinos
Pion (ฯ)
Kaon (ฮ)
Others
Proton
Neutron
Others
Mesons Baryons
Fundamental ParticlesSymbol Name Charge Baryon #
u Up +23
13
d Down โ13
13
c Charm +23
13
s Strange โ13
13
t Top +23
13
b Bottom โ13
13
Symbol Name Charge Baryon #
เดคu Antiup โ23 โ1
3
เดคd Antidown +13 โ1
3
เดคc Anticharm โ23 โ1
3
างs Antistrange +13 โ1
3
างt Antitop โ23 โ1
3
เดคb Antibottom +13
โ13
Symbol Name Charge Lepton #
e Electron โ1 1
ฮผ Muon โ1 1
ฯ Tau โ1 1
๐ฃ๐ Electron Neutrino 0 1
๐ฃฮผ Muon Neutrino 0 1
๐ฃฯ Tau Neutrino 0 1
Symbol Name Charge Lepton #
เดคe Antielectron (positron) +1 โ1
เดคฮผ Antimuon +1 โ1
เดคฯ Antitau +1 โ1
าง๐ฃ๐ Electron Antineutrino 0 โ1
าง๐ฃฮผ Muon Antineutrino 0 โ1
าง๐ฃฯ Tau Antineutrino 0 โ1
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
dางs
dเดคu
+1
3
โ1
3
โ2
3
โ1
3
0
-1
Quark Confinement
Quarks have never been observed on their own
dางs
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
างs
างs
d
Conservation
For an interaction to be possible, the following must stay conserved:
Baryon # Lepton # Charge Strangeness
๐ โ ๐ + ๐โ + าง๐ฃ๐Baryon # 1
Lepton # 0
Charge 0
1 0 0
0 1 -1
1 -1 0
This interaction is valid because all properties are conserved
Conservation
๐ + ๐ โ ๐+ + าง๐ฃ๐
๐ + ๐โ โ ๐ + ๐ฃ๐1 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
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 | Whatโs Wrong?
Whatโs wrong with these vertices?
No straight
lines
Both arrows
point intovertex
2 squiggles
at vertex
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 โbeforeโ condition.
e+
e-
ษฃ
before after
Match these!
a photon spontaneously
โpair producesโ 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
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