The Periodic Table gives the abbreviation for each element and how many protons are found in nucleus of that element. Atoms with the same number of protons but different number of neutrons are called isotopes. Even though there are 103 known elements there are thousands of isotopes. In nature atoms are mostly stable with a small portion that are unstable. An unstable atom has too much energy or is excited and wants to become a stable atom.
Radioactivity is a collection of unstable atoms that emit ionizing radiation to become stable atoms.
Or, the radiation may be so strong that it alters another atom s nucleus. Fission occurs when a neutron is absorbed into the nucleus of an atom and causes it to split. Half-Life One aspect of radioactivity is that atoms produce radiation to become stable over time. In other word, atoms of the same radioactive isotope do not emit radiation instantly. Half-life is the time in which half the atoms of a particular radioactive isotope decay into another atomic form.