Unit 2 - Particles Flashcards
when does radioactive decay occur?
when an unstable nucleus makes an attempt to become more stable.
what is Alpha decay (α)?
in this decay an alpha particle is emitted by the nucleus. An alpha particle is emitted by the nucleus consists of two protons and two neutrons (i.e. A helium nucleus).
what must be conserved when doing nuclear equations?
mass number and atomic number
what is Beta decay (β)?
takes place when a neutron in the nucleus decays into a proton and an electron The proton stays in the nucleus (so the atomic number increases by 1) while the electron is ejected from the atom’s nucleus as a beta particle.
what is Gamma decay (γ)?
Gamma rays are photons of electromagnetic energy; they are not particles. gamma rays are ejected from an atom’s nucleus
what are the two key processes which can result in the production of energy from the nucleus?
fission and fusion
define fission
a large atomic nucleus splits into 2 smaller nuclei and sometimes several neutrons. The smaller nuclei and neutrons that are produced gain large amounts of kinetic energy
what is fission simulated by Neutron Bombardment?
A neutron is “fired” at a uranium nucleus, causing the uranium nucleus to split. Smaller Daughter particles are produces as well as 3 further neutrons, all of which have a great deal of kinetic energy.
how can a fission reaction overheat?
One reaction produces several neutrons which can go on to cause further fission reactions. Left uncontrolled this leads to an ever escalating set of chain reactions and the reactor will eventually overheat.
how do we dispose of daughter particles from nuclear fission?
by burying it in shielded containers.
define nuclear fusion
2 small atomic nuclei combine to form a larger nucleus. Other small particles (such as neutrons) may also be left over.
where does nuclear fusion take place?
in stars like the sun
what are the conditions required for nuclear fusion to occur?
• High pressure (particles are closer together)
• High temperature (particles move faster)
Both of these increase the likelihood of collisions and therefore successful reactions.
what is plasma?
Under these high temperatures in fusion the electrons dissociate from their parent nuclei, leaving a mixture of highly charged particles
how is plasma controlled?
Powerful magnetic fields are used to control the path of the charged plasma. The fields can also be used to compress the gas,
why is mass lost in nuclear fission/fusion and how can this be calculated?
The “lost mass” is converted into kinetic energy of the products
E=mc2
what is the standard model?
the theory of fundamental particles and how they interact. Is explains existing particles and helps predict new particles we have not discovered.
What is antimatter?
Same mass but opposite charge to matter
What happens when antiparticles meet?
annihilate each other and their combined mass is converted into energy (E=mc2).
What are the two types of fundamental particles or fermions?
Leptons and quarks
6 types of leptons and 6 types of quarks
What are the six leptons?
Generation 1 - the electron (e) and its electron neutrino (νe)
Generation 2 - the muon (μ) and its muon neutrino (νμ)
Generation 3 - the tauon (τ) and its tauon neutrino (ντ)
Where are each generation of leptons found?
Generation 1 particles are found in ordinary matter, but generation 2 and 3 particles are mainly found in cosmic rays and particle accelerators.
What are quarks?
Quarks fall into the three generations and have not been found to exist on their own. Quarks only exist in bound states. Quarks have fractions of charges and must combine with others to form other particles with charge 1, a multiple or zero
What are the six quarks?
Generation 1 - the up (u) and the down (d) quarks
Generation 2 - the charm (c) and the strange (s) quarks
Generation 3 - the top (t) and the bottom (b) quarks
What charge does each quark have?
The up, charm and top all have a charge of +2/3. The down, strange and bottom all have a charge of -1/3.
Where are each generation of quarks found?
Only up and down quarks are found in ordinary matter. The other quarks are made in particle accelerators and may also exist in stars.
What are hadrons?
composite particles (particles made up of other particles). They are particles made from quarks
What are baryons?
Made from three quarks or three antiquarks
What are mesons?
Made of a quark and an antiquark
What charge must composite particles have?
A whole charge e.g. -2e,+1e
What are force mediating particles?
bosons: photons (electromagnetic force), W- and Z-bosons (weak force), and gluons (strong force).
What does beta decay provide evidence for?
The existence of the neutrino
