What is Radioactivity? Elements that are radioactive are UNSTABLE because they have too many nucleons or too much energy. In an attempt to become STABLE, they give up particles or energy and this IS RADIOACTIVITY From Latin radioto(to radiate)What is Radioactivity? Elements that are RADIOACTIVE are UNSTABLE because they have too many nucleons or too much energy. In an attempt to become STABLE, they give up particles or energy and this is……. RADIOACTIVITY From Latin radioto (to radiate)