Particles and nuclides

Electron info

Electrons orbit nucleus, electron is a fundamental particle

Plum pudding model

Represented atoms as tiny electrons embedded in positively charged background of uniform density

Specific charge

Ratio of charge to mass Q/m

What has largest specific charge

Electrons

Notation

A on top - protons and neutron's (mass number)

Z on bottom - number of protons (proton number)

An isotope

An atom of an element with a specific number of neutrons

Isotopes

Atoms of the same element with the same number of protons and different number of neutrons

Ions

Have different number of protons to electrons

Diameter of nucleus

Is of the order 10^-15m

Diameter of an atom

10^-10m

Repulsion and attraction strong nuclear force

Repulsive between 0 and 0.5fm

Attraction between 0.5fm and 3fm

Strong nuclear force function

Holds the nucleus together

How does nucleus stay together

Positive protons repel each other through electrostatic force

So held together by a stronger force through strong nuclear

This attracts neutrons to each other within a small range of distance between them

Types of radioactive decay

Alpha decay

B- decay

B+ decay

Alpha decay

Nucleus emits 4 2 a alpha particle with 2 protons 2 neutrons

Thing becomes new element bc dif number of protons

B- particle

B- particle is a high energy electron emitted

B- emitted from neutron rich nuclei

B+ particle

B+ particle is an antimatter electron, a positron

Emitted from proton rich nuclei

Need for neutrino

B particles emitted with range of possible energies

Neutrino also emitted: carries away balance of the energy so the total energy of the decay is always constant (principle of conservation of energy)

Existence of neutrino hypothesised to account for conservation of energy in beta decay

Gamma radiation

High energy penetrating electromagnetic radiation

Gamma decay

Nucleus loses energy but doesn't change to a different isotope

Antiparticles

Equal mass but opposite properties

eV to J

x 1.6x10^-19

energy of photon equation

rest energy of particles + surplus energy (appears as kinetic energy)

Pair production conditions

a particle-antiparticle pair may form from radiation if the energy of a photon is high enough (greater than 2mc squared = total rest energy)

what happens during pair production

photon converts all its energy into particle-antiparticle pair

annihilation

a particle and corresponding antiparticle collide and their mass becomes energy in two gamma photons travelling in opposite directions (to conserve momentum)

example of application of annihilation

PET scanner

four fundamental interactions

strong nuclear (strong interaction)

weak nuclear

electromagnetic

gravity

what do 4 fundamental forces act through

exchange particles

exchange particle for strong nuclear

pions moving between nucleons

exchange particles for weak nuclear

W bosons

exchange particles for electromagnetic force

virtual photons

strong nuclear force details

can be experienced by particles that contain quarks

involved in production of kaons

weak nuclear force

involved in B decay and in decay of particles with strangeness and where strangeness isn’t conserved

B+ decay diagram

B- decay diagram

electron capture diagram

proton-electron collision diagram

electron capture

proton in nucleus captures inner shell electron - decays into a neutron

electron capture features

occurs in nuclei which are proton rich

afterwards, an x-ray photon is emitted because an electron falls down through energy levels to fill vacancy left by captured electron, releasing energy as a photon

electron capture equation thing

AZ X + 0-1 e- becomes A Z-1 Y + neutrino

two electrons repelling each other diagram

two positrons repelling each other diagram

what are feynman diagrams used for

representing reactions or interactions in terms of particles going in and out, and exchange particles

2 classifications of a particle

hadron and lepton

2 classifications of hadron

mesons and baryons

free neutron info

unstable

decay via weak interaction forming proton, B- particle and electron antineutrino

quarks in B- and B+ decay

B- d quark changes into u quark, B+ u quark into d quark

what are virtual particles

real particles that exist for a very short time