Atoms, Nuclei and radiation

Experiment for existence and size of nucleus

Rutherford Scattering

• Fired alpha particles to gold foil

  • Most pass through no deflection: atom mostly empty space

  • Some deflect by small angle: Nucleus positively charged

  • Very few reflected back: Very small and dense nucleus

Model of an atom

• Nucleus: protons and neutrons

• Orbital electrons

Nucleon number

Number of protons and neutrons

Proton number

Number of protons in an atom

Isotopes

Atoms of the same element, same number of protons, different number of neutrons (different nucleon number)

What happens to nucleon numbers and charges in nuclear processes

Conserved

• No. nucelons (protons + neutrons) and leptons (electrons+neutrinos) of system conserved

Specific charge

Charge-mass ratio

• Charge/Mass

What group of fundamental particles do baryons and mesons belong to

Hadrons

• subatomic particles made up of quarks

Particles in baryons

• 3 quarks our 3 antiquarks

Particles that make up mesons

1 quark and 1 antiquark

Beta-plus decay

Proton turns into a neutron, emit positron and electron neutrino

• Up quark turns into down quark

Beta-minus decay

Neutron turns into a proton, emits electron and anti-electron neutrino

• down quark turns into up quark

Composition of proton

uud

Neutron composition

udd

Difference between leptons and quarks

Quarks interact with strong nuclear force, quarks do

Compare the properties of a quark and an antiquark

• Same mass

• Same magnitude of charge

• Both fundamental

• Opposite charge

What is a fundamental particle

• Particle which cant be broken down into anything smaller