Particles - Atomic Structure and Strong Nuclear Force
(SNF)
Definitions
• Nucleon – particle in the nucleus.
• Alpha particle – 2 protons and 2 neutrons.
• Alpha decay – nucleus ejects/loses 2 protons and 2 neutrons.
• Beta-minus particle – fast moving electron.
• Beta-minus decay – neutron becomes a proton, electron is ejected.
• Beta-plus particle – fast moving positron.
• Beta-plus decay – proton becomes a neutron, emits a positron.
• Neutrino - fundamental, neutral particle and has almost no mass.
• Gamma ray – a type of electromagnetic (EM) radiation of the highest energy and
shortest wavelength.
• Nucleon number – number of protons + neutrons in the nucleus.
• Proton number - number of protons.
• Isotope – an atom with the same number of protons, same number of electrons
but a different number of neutrons.
• Specific charge – charge per unit mass of a particle. Unit: Ckg-1.
• Photon – ‘chunk’ of wave energy.
• Rest energies – the energy a particle has when stationary. The E in E=mc2.
• Electron Volt (eV) – the energy gained by an electron as it moves across a
potential difference (pd) of 1 volt (1V).
• Annihilation: particle meets an antiparticle, mass is converted into energy (two
photons).
• Pair Production: a photon is converted into a particle and antiparticle.
SNF acts between all nucleons. SNF at a distance of less than 0.5fm is repulsive, from
0.5-3fm is attractive, after 3fm is weak and gets closer to 0.
Problem with alpha decay then beta decay
Alpha decay was monokinetic (took the same amount of energy that was available
(conservation of energy)), whereas, in beta decay there was a range of energy values.
Solution with alpha decay then beta decay
It was theorised (in 1932 by Wolfgang Pauli, observed for the first time in 1956) that
another particle with ALMOST zero mass was emitted with the beta particle, which took
any energy not given to the beta particle, this led to the discovery of the neutrino.
(SNF)
Definitions
• Nucleon – particle in the nucleus.
• Alpha particle – 2 protons and 2 neutrons.
• Alpha decay – nucleus ejects/loses 2 protons and 2 neutrons.
• Beta-minus particle – fast moving electron.
• Beta-minus decay – neutron becomes a proton, electron is ejected.
• Beta-plus particle – fast moving positron.
• Beta-plus decay – proton becomes a neutron, emits a positron.
• Neutrino - fundamental, neutral particle and has almost no mass.
• Gamma ray – a type of electromagnetic (EM) radiation of the highest energy and
shortest wavelength.
• Nucleon number – number of protons + neutrons in the nucleus.
• Proton number - number of protons.
• Isotope – an atom with the same number of protons, same number of electrons
but a different number of neutrons.
• Specific charge – charge per unit mass of a particle. Unit: Ckg-1.
• Photon – ‘chunk’ of wave energy.
• Rest energies – the energy a particle has when stationary. The E in E=mc2.
• Electron Volt (eV) – the energy gained by an electron as it moves across a
potential difference (pd) of 1 volt (1V).
• Annihilation: particle meets an antiparticle, mass is converted into energy (two
photons).
• Pair Production: a photon is converted into a particle and antiparticle.
SNF acts between all nucleons. SNF at a distance of less than 0.5fm is repulsive, from
0.5-3fm is attractive, after 3fm is weak and gets closer to 0.
Problem with alpha decay then beta decay
Alpha decay was monokinetic (took the same amount of energy that was available
(conservation of energy)), whereas, in beta decay there was a range of energy values.
Solution with alpha decay then beta decay
It was theorised (in 1932 by Wolfgang Pauli, observed for the first time in 1956) that
another particle with ALMOST zero mass was emitted with the beta particle, which took
any energy not given to the beta particle, this led to the discovery of the neutrino.
