Radioactive decay
Nuclide stability
Nuclei that lie on the stability line are stable nuclei.
Nuclei that lie above the line of stability = too many neutrons to be stable (“neutron-rich”).
Will release neutrons in order to gain stability.
Nuclei below the line of stability = too many protons to be stable (“proton-rich”).
Natural radioactive decay
Random
Spontaneous
Cannot affect probability of a nucleus decaying
Cannot predict when/which nucleus will decay
Not affected by the presence of other nuclei
Not affected by a change in chemical or physical factors
Types
Alpha-decay
Release of helium nucleus
Stopped by paper
Very high ionizing ability
Beta-minus decay
Release of an electron and electron anti-neutrino
Stopped by 1mm akunibun
Low ionizing ability
Gamma decay
Release of a photon from a nuclide with an energy surplus
Goes through several cm of lead
High ionizing ability
Prediction of existence of antineutrino
Conservation of energy, momentum and charge were used.
Mathematics of decay
Definitions
Half-life: The time taken for half the original nuclei to decay.
Activity: The number of disintegrations per unit time , also known as the decay rate.
Decay constant: The probability per unit time that a nucleus will decay.
Radioactive decay shows an exponential relationship
Formulae:
Will release protons in order to gain stability.
When beta particles were first discovered, it was noticed that they were emitted with a range of speeds
Some other particle must be carrying off some of the energy and momentum released in the decay.
This particle is now known as the antineutrino (or more correctly, the electron antineutrino), with symbol ν ̅_e.
Neutrinos have very little mass and no electric charge, which makes them very difficult to detect.