Radiotherapy: Nuclear Stability and Radioactive Decay

Vocabulary flashcards covering nuclear stability principles, decay modes, and particles based on the Radiotherapy lecture notes.

Nuclear Stability factors

The stability of a nucleus depends mainly on $A$ (mass number) and $Z$ (atomic number).

n:p ratio ($N/Z$)

The ratio of neutrons ($N$) to protons ($Z$) which is key to nuclear stability.

Stable light atoms

Atoms where the ratio of $N/Z$ is approximately $1$.

Stable heavier atoms ($Z > 20$)

Nuclides where the number of neutrons must increase to stabilise the atom, requiring an $n:p$ ratio of $1.15-1.5$.

Unstable nuclides threshold

The point at which all nuclides are unstable, occurring when $Z > 83$.

Selection for stability

There is a strong selection for even numbers of both $N$ and $Z$, as unpaired nucleons are less stable.

Alpha emissions (heavy nuclides)

A process used by very heavy nuclides to decay in order to reduce both $N$ and $Z$.

Radioactive Decay

The process in which an unstable atomic nucleus spontaneously loses energy by emitting ionising particles and radiation.

Isotopes of $Z < 84$ (decay)

Radioactive changes involving the conversion from one type of nucleon to another.

Isotopes of $Z > 83$ (decay)

Radioactive changes that may involve a reduction in the number of nucleons in the nucleus.

Neutron rich nuclides

Nuclides that undergo $-1\text{beta}$ decay, which converts a neutron into a proton to shift the $N/Z$ ratio to the band of stability.

Proton rich nuclides

Nuclides that undergo $+1\text{beta}$ decay or electron capture to convert a proton to a neutron.

Parent nuclide

The original atom of one type that transforms to a different type during radioactive decay.

Daughter nuclide

The atom of a different type produced as a result of the transformation of the parent nuclide.

Alpha decay

A decay process where a nucleus allows $2$ protons and $2$ neutrons to escape, resulting in a smaller nucleus with a more stable arrangement.

Alpha particle

A particle generated from nuclear decay containing $2$ protons and $2$ neutrons (helium-$4$) with a charge of $+2e$.