Particles

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  • Created by: Park-lyf
  • Created on: 28-01-16 17:24

Definitions

Nucleon- particles that reside within the nucleus (proton and neutron)

Isotopes- Forms of an element with the same proton number but different nucleon numbers 

Anti particle- A 'Mirror image' of a particle with identical mass but opposite charge 

Annihilation- The conversion of mass of a particle and its antiparticle to a pair of photons of electromagentic radiation 

Pair production- The process of a photon of electromagnetic energy is converted to a pair of particles 

Neutrino- fundamental particle with no charge 

Exchange particle- Virtual particle, may exist for a very short time and is a force mediator 

Conservation of charge- total charge after reaction is smae as total charge before reaction 

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Inside the nucleus

A neutral atom has no net charge, this is due to the number of protons being balanced by the number of electrons orbitting the atom. 

Holding the nucleus together is positive charges repelling each other, and at short distances electrostatic forces pushing the nucleus apart. Another that acts inside the nucleus known as the strong force, it has a short range and no effect on seperations greater than 5fm, it is an attractive force until the separation is less than 1fm (it then becomes v repulsive). Its overall efect is to pull nucleus together, however the repulsion keeps it from collapsing. 

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Isotopes

Isotopes are forms of an element with the same proton number but different nucleon numbers 

Different isotopes of an element have identical chemical behaviour as their atoms have same number of electrons.

Isotopes also have same number of protons in their nucleus, difference is simply number of neutrons (makes some isotopes heavier than others) 

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Pair production

The opposite process to annihilation is pair production where matter is produced from energy. 

In pair production two particles are always created, one being a conventional particle and one being its antimatter twin. After pair production there is always one positive and one negative particle so the overall charge is 0

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Neutrinos

Probably the most abundant particles in universe, outnumber protons and neutrons. They are emitted by radioactive nuclei and form nuclear reactions. 

Neutrinos and antineutrinos are difficult to detect due to their lack of charge. Neutrinos interract with other matter very weakly.

Neutrino is a fundamental particle which carries no charge and mass that is much less than that of an electron. 

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Fundamental forces

Forces that hold various particcles in the nucleus together in an atom

Gravity- Infinite range, acts in all particles, on an atomic scale it has negligible influence as it the weakest fundamental force 

Electromagnetic force- Acts between all charged particles, holds atoms and molecules together 

Weak interraction- Acts between all particles over short range, responsible for radioactive decay 

Strong interraction- the strong interraction holds neuclei together, it acts between hadrons (neutrons or protons) short range, the strong force is not felt by leptopns 

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Classification of particles

Current theories suggest there are only 3 families of fundamental particles 

Leptons 

Quarks

Gauge Bosons 

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Leptons

12 different members of lepton family, three being types of electrons, (electron muon and tau) three types of neutrinos and all their antiparticles

All leptons are fundamental particles 

The Muon- close relative of the electron, carries same charge as electron but possesses a mass 207 times bigger 

Leptons and antileptons are fundamental particles 

Three charged leptons; electron, muon and tau 

each of these has an associuated nutrino 

each has an antiparticle 

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Hadrons

Possess a much greater mass than leptons (Pi mesons, Kaons, delta mesons)

They are divided into 2 groups 

Baryons; proton, neutron and their antiparticles

Mesons; pi/pi meson- takes 3 forms (positive, negative and uncharged), k meson/kaon

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Quarks and antiquarks

All hadrons are composed of smaller constiuents called Quarks 

There are 3 different types of quark; up, down and strange alongside their antiquarks 

Baryons are combinations of three quarks 

Antibaryons consist of three antiquarks

Mesons are composed of a quark and an antiquark

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Equations

Specific charge is calculated by dividing charge by mass, its units are C/KG-1

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