7 - Atomic, nuclear and particle Flashcards
What did Rutherford’s experiment show?
the atom is mostly empty space
the mass of the atom is within the nucleus
deflected beam of particles must have approached positively charged region - the nucleus
volume of nucleus is very small
What are electron energy levels?
specific energies electrons in an atom can have
What causes an electron to be excited?
absorption of energy
What causes an electron to be relaxed?
emission of energy
What is the ground state?
13.6eV - the lowest energy level
What is the first excited state?
3.4eV
What is the second excited state?
1.5eV
What is the ionisation level?
0eV - the highest energy level, at which, the electron can escape the atom, forming an ion
What is activity?
the number of nuclear disintegrations per second
What is activity measured in?
Bequerels, Bq
What is alpha decay?
an element decays to produce a different element and an alpha particle, consisting of two protons and two neutrons
What is gamma radiation?
an EM wave emitted due to transitions in the nucleus
often accompanies alpha and beta decay
What is beta + decay?
a proton decays into a neutron, a positron and a neutrino
What is beta - decay?
a neutron decays into a proton, an electron and an anti-neutrino
What is beta?
a fast moving electron
What is an electron volt?
a unit of energy
KE electron gains by travelling across a pd of 1 volt
1eV = 1.6x10^-19C
What is the equation for energy gain?
energy gain = voltage x charge
What is half-life?
the time for half the radioactive isotopes to decay
What are quanta?
discrete packets of the EM spectrum
measurement of quantity
What are photons?
the smallest discrete amount of EM radiation
elementary particle
What is the energy carried by quantum?
E = hf h = Planck's constant 6.63 x 10^-34Js f = frequency
What is an electronvolt?
an alternative unit of energy
the KE electron gains travelling across a pd of 1 volt
What is the equation for energy gain?
E = VQ
What is strong force?
the force which exists within the nucleus to hold protons and neutrons together
What is the mass defect?
the difference between mass of the nucleus and mass of the individual particles
What is the binding energy?
the energy needed to separate the nucleus into individual particles
How does the binding energy of the particles change after nuclear fission?
heavier elements are split into lighter elements, with lower binding energy per nucleon
How does the binding energy of the particles change after nuclear fusion?
lighter nuclei are joined to form a heavier nucleus with higher binding energy per nucleon
What are the characteristics of hadrons?
affected by strong force
made of quarks
relatively heavy
What are the characteristics of barions?
hadrons
made of three quarks
relatively heavy
What are the characteristics of mesons?
hadrons
intermediate heaviness
made of one quark, one anti-quark
What are the characteristics of leptons
not affected by strong force
indivisible
relatively light
What is the charge on an up quark?
+2/3
What is the charge on a down quark?
-1/3
What is the charge on a strange quark?
-1/3
What is the charge on an anti-up quark?
-2/3
What is the charge on an anti-down quark?
+1/3
What is the charge on an anti-strange quark?
+1/3
Which quarks is a proton made out of?
u u d
Which quarks is a neutron made out of?
u d d
Which quarks is a pion+ made out of?
u /d
Which quarks is a pion- made out of?
/u d
Which quarks is a pion0 made out of?
either u /u or d /d
Which quarks is a kaon+ made out of?
u /s
Which quarks is a pion- made out of?
s /u
Which quarks is a kaon0 made out of?
d /s
Which quarks is a /kaon0 made out of?
s /d
What is anti-matter
for each matter particle, there is corresponding anti-particle
same mass as corresponding particle but opposite charge
when a particle and anti-particle meet, they annihilate and produce two photons
Which leptons are electrically charged?
electrons, muons and taons
Which leptons have zero mass and zero charge?
electron neutrino
muon neutrino
tau neutrino
What are leptons?
elementary particles
not affected by strong force
What are the characteristics of strong force?
attractive forces between nucleons p-p and n-n repulsive at ranges less than 1fm range doesn't extent beyond a few nm doesn't depend on charge of nucleus readily saturated by surrounding nucleon
What virtual particle is exchanged in gravitational force?
graviton
What virtual particle is exchanged in electostatic force?
photon
What virtual particle is exchanged in strong force?
gluon
What virtual particle is exchanged in weak force?
W+, W-, W0 bosons
What must be conserved for an equation to be possible?
charge, lepton number and baryon number
Which force are neutrinos affected by?
weak force
Which reactions conserve strangeness?
any involving strong force or weak force
What does the x axis of a Feynman diagram represent?
time
What does the y axis of a Feynamn diagram represent?
the space dimension
What is an electron moving to the right equivalent to?
a positron moving to the left
What does a squiggly line represent?
a photon
What are the implications of quark confinement?
quarks cannot be directly observed as free particles
must remain bound to other quarks
