What is radioactivity?
The emission of ionizing particles...
Radioactivity is the tendency of an atom to emit ionizing radiation in the form of ionizing particles, sich as alpha or beta particles, or even rays like gamma rays. Higher radioactive substances are usually unstable isotopes, such as isotopes with a lot of neutrons in them.
I'm pretty sure everyone has heard of the element uranium. It is weakly radioactive, having a life span of around
Hope this helps!