Radiation chart of nuclides

Nuclear Radiation

Chart of the Nuclides


The Chart of the Nuclides is important to understand because it is a common tool used in the radiation industry

The Chart is similar to the periodic table in that it lists all known elements, atomic #’s, atomic mass, etc.

However, it also gives all the different known isotopes for each element

The Chart is in reality a graph of all the known nuclides graphing proton # vs. neutron #


The row #’s are equivalent to the atomic number of the element

Thus each row, represents a different element

The column #’s are equivalent to the neutron numbers of the nuclides


The first box in each row is a label for that row, it is not a nuclide

The information given in that box includes.. The chemical symbol & name of the element The atomic mass of the element The absorption cross section in the units of

Barns () A Barn is a unit of area which is determined

by the diameter of the nucleus


Stable nuclides are gray colored boxes, they contain… The chemical symbol of the element The number of nucleons (Protons + Neutrons),

which equals the atomic mass The % of abundance in nature And the capture cross section in Barns ()

The plot of all the stable nuclides, called the line of stability, forms a linear plot ~ 45º


Unstable nuclides are indicated by all the other boxes shown on the chart

Each of those boxes contain… The chemical symbol of the element The number of nucleons, or atomic mass The half-life of the nuclide

a – years, d – days, h – hours, m – minutes s – seconds, ms – milliseconds, s – microseconds ~ - approximately

Half-Life

• Half-life, t1/2, is the time required for half the atoms of a radioactive nuclide to decay.

• Each radioactive nuclide has its own half-life.

• More-stable nuclides decay slowly and have longer half-lives.

Click below to watch the Visual Concept.

Half-Life

Potassium-40 Half-Life

Rate of Decay

Half-Lives of Some Radioactive Isotopes


Mode of decay i.e. - alpha, - beta, It – Isomeric Transition

Energy of decay, given in MeV - gamma emission, which is a result of decay Gamma energies in KeV


Another type of nuclide shown on the chart are those that undergo isomeric decay

Isomeric decay results from a nuclide giving off an alpha or beta and becoming a metastable form

These atoms will give off energy like a gamma when they de-excite at a later time

These are shown on the chart as a box inside a box


Some radioactive nuclides can undergo what is called “branching” decay

This means that under some circumstances they can give off one form of radiation, but under other circumstances they give off another Example – Copper 64, gives off beta – or beta +

Both modes of decay will be given in the box on the chart


Using the Chart of the Nuclides we can easily tell what a radioactive isotope changes into after decay

By moving from box to box based on whether or not protons or neutrons are lost or gained as a result of radiation release, we can determine the resulting isotope


Using this information you can follow radioactive decay until it reaches stability

In nature, there are three naturally occurring decay chains

They each begin with nuclides that have long enough half-lives that they have been present since the formation of the Earth


As the nuclides in the decay chains release radiation, they change into other nuclides that are also radioactive

They continue this process until they reach a stable isotope (usually lead) i.e. All of the Uranium 238 on the earth will

eventually become lead


There is another decay chain that was created with the beginnings of nuclear energy (Man Made)

It is called “Transuranic Decay Chain” and begins with the element Plutonium

This leads us into the two activities which use the Chart of the Nuclides Activity 1 & 2 pp 117 - 119

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Radiation chart of nuclides