Question

A radioactive nucleus A finally transforms into stable nucleus B . then A and b are called?

Answer 1

Nuclei

Answer 2

what i want is something starting with iso(tone/bar/top......)

Answer 3

Ah i believe what you want is isomer however that is a metastable state of the nucleus not a before or after state

Answer 4

ah just remembered your before state is an isotope

Answer 5

A and B are known as isotopes. However, they do have descriptive names. In this example A would be known as the parent isotope, and B would be the daughter isotope.