Download The Standard Model of the Atom

Modern Studies of the Atom
Hideki Yukawa- 1935- Theorized that a
particle passes back and forth between
protons and neutrons to hold the nucleus
together.
Predicted the existence
of a particle called a
meson (also known as
pions). The meson was
observed in 1947.
Enrico Fermi-1934- Theorized that a neutral
particle is emitted during beta decay which he
called the neutrino.
Cs → Ba + e− + ν (beta decay)
electron
neutrino
Neutrino- tiny neutron – Observed in 1956
Radioactive Decay
Alpha
_________
Beta
Gamma
_______
_____
Paul Dirac -late 1920s
Theorized that electrons
should be expected in two
energy states, one
positive and one negative.
He called these
antiparticles.
Antiparticles-Mirror image of each particle.
Particle have the same mass but the
opposite charge.(ie: electron and positron)


e  e  2hf
Depends on frequency
When Matter meets antimatter annihilation
occurs. Energy and radiation is given off.
 rays  e   e 
When gamma rays pass close to nucleus, a
particle and antiparticle are formed.(requires
1.02MeV or more of energy)
The Standard Model
Matter
Particles made of
quarks
Protons and
neutron
Hadrons
Baryons
Mesons
3 Quarks
2 quarks
Leptons
electrons
QUARKS
Fundamental particle of the
standard model.
6 types or flavors.
Have charge.
Can’t exist on their own.
Make up Baryons and Mesons.
TERMS
Hadrons- anything composed of quarks
Mesons-subatomic particles composed of a
quark and antiquark.
Baryons- particles formed by three quarks.
Includes protons and neutrons.
Leptons- Doesn’t have quarks. Includes
electrons, muons, Tau, neutrino
and antiparticles.
QUARKS
Up (u)
+2/3
Down(d) -1/3
Charm (c) +2/3
Strange(s) -1/3
Top (t)
+2/3
Bottom (b) -1/3
DATES OBSERVED
up- 1964
Down- 1964
Strange- 1964
Charm-1975
Bottom- 1977
Top- 1995
Neutrons are made of 2
down quarks and one up
quark. (udd)
(+2/3) + (-1/3) + (-1/3) = 0
Protons are made of 2 up
quarks and one down quark.
(uud)
(+2/3)+(+2/3)+(-1/3) = +1
Strong Force-Short range
force that holds quarks
together to form protons and
neutrons in the nucleus.
Electromagnetic forceAttractive and repulsive
force between charges.
Binds the electrons to the
nucleus.
Weak Force- Responsible for
formation of elements and
release of nuclear energy and
beta decay.
Gravitational force-Weakest
of four forces. Force due to
the mass of the atom.
Gluon- the exchange particle between
quarks
Higgs Boson
Higgs Boson- subatomic
particle with zero electric
charge and mass greater than
zero. Its thought to interact
with other particles to give
them mass.
Observed at CERN on July 4th,
2012.
The Higgs boson would help
explain the origin of mass in
the universe. The Higgs boson
completes the standard model.
PARTICLE ACCELERATORS
Cyclotron- E.O. Lawrence
accelerated protons to a
very high speed and
projected them into a
stationary target.
Synchrotron
Similar to a Cyclotron.
Particle experience a
higher magnetic field
therefore moves at a
higher speed.
Fermi National Accelerator
Lab- Batavia IllinoisTevatron- 4miles wideAccelerates protons to 99.9%
speed of light. Uncovered the
top quark
Linear Accelerator
Particles are accelerated
as they pass through a
series of conductors.
Longest is in Palo Alto
California. Its 3.3 km
long and buried 7.6m
underground.
Particle Colliders
Instead of a stationary
target, this aims two high
speed particles at each
other and detects particles
that are emitted.
CERN- French-Swiss collider
that is sponsored by 19
European countries in
hopes of locating the HiggsBoson particle. (17miles
wide and 574ft deep)
Standard Model Limitations
• The standard model doesn’t predict the mass of
the fundamental particles that make up
luminous matter.
• Doesn’t predict the existence of dark matter
• Key particles have not been directly observed.
Their existence is inferred by experimental
observations.
• 1% discrepancy in how the neutrino behaves.
Due to results, they feel there may be an
unknown force or particle influencing it.
Dark Matter
• Dark matter is matter that
doesn’t emit or scatter light
or other electromagnetic
radiation. It cannot be
directly detected. Dark
matter is believed to make
up 83% of the matter in the
universe and 23% of the
mass-energy.
• Regular Matter makes up
only 17% of all matter.
Dark Matter is not….
• Is not in the form of mass that we see.
• is not made up of baryons. We know this
because we would be able to detect baryonic
clouds by their absorption of radiation passing
through them.
• dark matter is not antimatter, because we do
not see the unique gamma rays that are
produced when antimatter annihilates with
matter.
Unanswered questions
• Is there only one type of Higgs Boson?
• Are protons absolutely stable? If not, then
what is the proton‘s half-life?
• Why is there now more detectable matter
than antimatter in the universe?
• What governs the transition of quarks and
gluons into mesons and baryons?
• What is the nature of the nuclear force that
binds protons and neutrons into stable nuclei
or rare isotopes?