Topic 7 Atomic, Nuclear and particle physics Flashcards
What did Rutherford’s experiment achieve?
It proved the existence of the nucleus
Why did they use alpha particles in Rutherford’s experiment?
- The mass was large enough to not be deflected by electrons
- It is positively charged to investigate the charge distribution
Describe Thompson’s Plum Pudding Model
Atoms were thought to be a cloud if positive charge with negative charges embedded in it
Isotope definition
Isotopes are different nuclei of an element that have different number of neutrons (but same number of protons)
Nucleon definition
A nucleon is any particle in the nucleus (ie. proton or neutron)
What is a strong nuclear force
Protons and neutrons are held together by a strong nuclear force which:
- is balanced by repulsion between protons which acts at a long range (Coulomb interaction)
- Acts at a short range ie. protons and neutrons must be adjacent
Describe band of stability
As the atom gets larger, it requires more neutrons, if not, the nucleus decays to form more stable smaller nuclei (radioactivity)
What is a alpha particle
Helium nucleus
What is beta -ve decay
An electron emitted from the nucleus (neutron => proton)
What is beta +ve decay
Emits a positive electron or positron (proton => neutron)
what is an alpha particle’s range in air
5cm
what is a beta particle’s range in air
30cm
what is a photon particle’s range in air
can be hundreds of meters
what stops alpha particle’s radiation
a piece of paper
what stops beta particle’s radiation
1mm of aluminium
what stops photon particle’s radiation
10cm of lead
What is ionisation
The removal of an electron from an atom or molecule
What accompanies beta -ve decay
Antineutrino
What accompanies beta +ve decay
Neutrinos
Half-life definition
The time taken for half of the nuclei in a sample to decay. It is spontaneous and random
What are the effects of radiation
- cells are damaged but repair themselves correctly
- cells are damaged but repair themselves incorrectly
- cells die
Transmutation definition
Nuclei change from one element to another by the addition of nucleons. Can occur naturally or spontaneously
Nuclear fission
Large nuclei are broken down into smaller nuclei by being bombarded with neutrons or alpha particles. This is how energy is produced in nuclear power plants.
Nuclear fusion
Small nuclei are combined to form larger nuclei if temperature and pressures are high enough to give them the energy to overcome electrostatic repulsion between them.
unified atomic mass unit (u)
it is equivalent to the mass of 1/12 of a 12C atom
Mass defect
the difference in mass between individual nucleons and their total mass when bound
binding energy
the amount of energy required to break apart a nucleus into seperate nucleons
binding energy per nucleon (bepn)=
total binding energy / number of nucleons
the greater the binding energy per nucleon, _______________
the more stable the nucleus
what is the most stable atomic nucleus
56Fe
energy released =
total binding energy of PRODUCTS –total binding energy of REACTANTS
what happens when a particle and an anti-particle combine?
they annihilate each other and their total mass is converted to energy in the form of a pair of photons
what family are leptons a part of
electron
name all the quarks
up
down
strange
charm
top
bottom
what are hadrons
groups of quarks
meson definition
formed from quark-antiquark pairs
baryon definition
formed from 3 quark or 3 antiquarks
why can quarks not exist alone
if two quarks move apart, energy is required. the further they move apart, the more energy must be put in. this energy, however, does not break the forces between the quarks but instead is converted into mass and produces a new quark
what baryon number does a anti-quark have
-1/3
what quarks does a proton consist of
uud (up up down)
what quarks does a neutron consist of
udd (up down down)
what is a virtual particle
they cannot be detected during their transfer between particles because detection would mean that it is no longer acting as a mediator between the particles
what is the purpose of a gauge boson
they mediate (or transmit) forces between particles; the larger the mass, the shorter the range
what hold hadrons together
gluons
gluons are in-between
what is the purpose of gluons
to hold hadrons together
what keep a number of hadrons together
pions (pi mesons)
pions are across
what do W+ and W- bosons do
they transfer charge between weak interaction
what do Z0 bosons do
they transfer momentum and energy
what is conserved during any vertex (interaction between particles)
- charge
- lepton number
- baryon number
- mass-energy
- momentum
- strangeness is only conserved with strong interactions (between quarks)
what is the Higgs boson
the reason by which particles acquire mass. particles gain mass by interacting with this boson. due to its high mass a great deal of energy was required to produce the Higgs boson
what fundamental force acts on quarks (not leptons)
strong nuclear force
what fundamental force acts on leptons and quarks
weak nuclear force
what is a beta particle’s range in air
30cm
how do you convert eV to J
times by 1.6 x 10^ –19
how do you convert J to eV
divide by 1.6 x 10^ –19
how do you convert MeV to eV
times by 10^6
