Nuclei and Particles Flashcards
Atomic Mass (A), Atomic no (Z)
A=protons+Neutrons, Z=Protons
Isotope
Same element, different atomic mass. different no of neutrons
isotope notation
2 numbers in front of element symbol (upper for atomic mass, lower for atomic no)
Nucleon
collective name for protons and neutrons
Ion
one or more electrons added or removed from neutral atom….electrically charged ion formed
speed of light
3 x 10^8 ms-1
energy and mass interchangeable due to e=mc^2
so can refer to subatomic particles by their energy not mass (mass energy). MeV mega electronvolts). Or expressed as E/c^2 in keV (kilo electron volts (thousand electron volts)
Proton mass
proton almost 2000 times more massive than electron
Antimatter
Same mass as matter counterparts, but attributes have opposite sign (eg electron charge)
positron
Antimatter counterpart of electron
antiproton
Antimatter counterpart of proton
Matter - antimatter annihilation
Collision between matter and antimatter. particle + antiparticle…photons. Large amount of energy
Pair production
photons…Particle + antiparticle
Energy time uncertainty principle.
Time a particle can exist with “borrowed” energy. Rearranged to delta t = h/(4pi x delta E) to find time…orig eq: delta E x delta t is approx = to h/4pi
Quantum jump
Occur between energy levels. For nuclei, gamma ray photons emitted, hundreds of thousands of times more energy than with visible photons. 1MeV(mega electron volt) compared to 2 or 3 eV
Mass defect, binding energy
Amount by which the nucleus is less massive than its constituent parts. Binding energy also this amount, so also the same amount of energy need to break apart the nucleus
Alpha decay and particle
Emitted during decay,same as helium nucleus, 2 protons 2 neutrons
Binding energy of alpha particle
28.3 meV
Beta decay
Transformations between neutrons and protons at the heart of it. Beta - decay, beta + decay, electron capture all types of beta decay
conservation in nuclear processes
mass, energy, net charge conserved
Beta minus decay
Neutron to proton, electron and electron antineutrino (zero charge) created. Extra proton, 1 less neutron so atomic mass same, atomic no +1.
Beta plus decay
Proton to neutron, so atomic no -1. Positron (+ as antielectron) and electron neutrino (zero charge) created
Electron capture
Nucleus captures an electron, proton interacts with electron forming a neutron, emitting electron neutrino. Atomic no decreases by 1
Gamma decay
Nucleus in excited state (from decay), quantum jump to lower energy state, photon emission. Similar process to atoms but gamma ray photon about a million times larger
Half life
p=(1/2)^n p_0 n=no of half lives elapsed, p_0 is original amount of atoms (1/2)^n fraction remaining after n no of half lives. D/P = 2^n -1 to work out no of half lives elapsed (d, daughter, p parent)
Nuclear fission
Relatively massive nucleus splits
Nuclear fusion
2 or more low mass nuclei join together to form a heavier nucleus
Neutrino
As neutral charge, not affected by electromagnetic forces which act on electrons, so can pass through greater distances in matter
Leptons
Muon, Tauon, Lepton. muon neutrino, Tauon neutrino, electron neutrino. There is an antilepton antimatter particle for each, with opposite charge (if charges as in electron ,muon and tauon)
Quarks
Combine to form hadrons (protons and neutrons are hadrons). Up, down, charm, strange, top, bottom are the 6 flavours of quarks.u,c,t pos charge 2/3e, d,s,b neg -1/3e charge. Antiquark for each. up and down make up protons and neutrons
Hadrons
Made up of Quarks and Antiquarks. 3 quarks = baryon, 3 antiquarks = antibaryon, 1 quark, 1 antiquark = meson. Protons and neutrons are baryons.
Particle generations
12 fundamental particles (6 leptons, 6 quarks plus their antiparticles). Almost everything made up of first generation leptons and quarks (electrons, up and down quarks, electron neutrinos being created in decay). 2nd gen: Muon, muon neutrino leptons, charm and strange quarks. 3rd gen: Tauon, tauon neutrino, top and bottom quarks
High energy particle reaction rules
Quantum indeterminacy as to what is produced…but 3 rules. Energy conserved, electric charge conserved, no of quarks - no of antiquarks conserved
Quarks do not come out in collision
Their KE is transformed into mass of new hadrons
Strong interaction
Mechanism for strong nuclear force, binds quarks together, residual strong interaction binds nucleus in nuclei
Gluons
Elementary particle, acts as exchange particle for strong force between quarks. Holds quarks together, sometime emitted by quarks after collision. Zero electric charge. Carry a combination of colour and anticolour charge
Quantum Chromodynamics (QCD)
Quantum theory of the strong interactions between quarks and gluons. Colour charge. Red, Green, Blue, each + or -. Opposites are antired (cyan), Antigreen (magenta), Antiblue (yellow). Carried by gluons. Leptons and photons have no colour charge. Colour charge conserved in strong interactions. Baryons have quarks 1 of each colour (neutral charge as red + green + blue = white). Antibaryons have neutral charge as 1 of each anticolour. Mesons 1 colour 1 anticolour so neutral.
Only particles with net colour charge of zero can exist in an independant state.
So gluons can’t or quarks on their own
Neutron and Proton quark composition
neutron udd, proton uud
Beta decay at quark level
Quark conversion at heart of it all, as down quark converts to up quark (neutron to proton)
Quanta involved in electromagnetic, strong, weak interactions
electromagnetic - photons, strong - gluons, weak - W and Z bosons
Weak interaction
All 3 types of beta decay are weak interactions. W and Z bosons created (they have large masses so need more energy in the system to create). If easier to create, decay would be much quicker and we wouldnt exist without the W boson! (neutrons would have decayed very quickly after the big bang)
SUMMARY
Leptons, quarks and hadrons:
There are six flavours of lepton, the lightest of which are the electron and electron neutrino; there are six flavours of quark, the lightest of which are the up and down quarks.
All leptons and quarks have corresponding antiparticles with the same mass but opposite electric charge and colour charge (in the case of quarks).
Combinations of three quarks are called baryons; combinations of three antiquarks are called antibaryons; combinations of a quark and an antiquark are called mesons.
As examples, a proton has the quark composition ‘uud’; a neutron has the quark composition ‘udd’; pions are mesons composed of up and down quarks and antiquarks.
Strong and weak interactions:
The strong interaction binds quarks together inside nucleons, and binds nucleons together inside nuclei; all strong interactions involve gluons.
Quarks and gluons each carry a colour charge; baryons, antibaryons and mesons are all colour-neutral.
In strong interactions: energy, electric charge, colour charge and the number of quarks minus the number of antiquarks are all conserved.
The weak interaction allows leptons and quarks to change flavour; all weak interactions, such as beta-decay, involve W or Z bosons.
In weak interactions, energy, electric charge, the number of quarks minus the number of antiquarks, and the number of leptons minus the number of antileptons are all conserved.
