Neutron interactions with most types of matter in this manner usually produce radioactive nuclei.

One unique concern was the age of the galaxy as measured by the remaining amount of radioactive nuclei.

He suggested putting a cat in an enclosed box, and also a device which would detect the decay of a single radioactive nucleus.

In most cases this more stable configuration yields a radioactive nucleus.

There is a gun pointing at it, and it will go off if a radioactive nucleus decays.

"An explanation for the decay of radioactive nuclei and the like, perhaps."

This means that we cannot predict exactly when any specific radioactive nucleus will decay.

This could be numerous chemical elements with various radioactive nuclei.

They aim at studying the nuclear structure of radioactive nuclei.

Such radioactive nuclei can exhibit half-lives ranging from small fractions of a second to many years.