n. 1  The charter that King John of England issued in 1215 at the behest of his barons, recognizing the right of persons to certain basic liberties, such as due process, later also embodied in the American Constitution: We are heirs to a tradition given voice 800 years ago by Magna Carta, which ...
Radioactive decay occurs in unstable atomic nuclei â that is, ones that donât have enough binding energy to hold the nucleus together due to an excess of either protons or neutrons. It comes in three main types â named alpha, beta and gamma for the first three letters of the Greek alphabet.Alpha decay.fter a nucleus undergoes alpha or beta decay, it is often left in an excited state with excess energy. Just as an electron can move to a lower energy state by emitting a photon somewhere in the ultraviolet to infrared range, an atomic nucleus loses energy by emitting a gamma ray.
Isotopes utilized in nuclear medicine fall into two broad categories: Stable and Unstable. Stable isotopes do not undergo radioactive decay. WHAT IS A STABLE ISOTOPE? A stable isotope is any of two or more forms of an element whos nuclei contains the same number of protons and electrons, but a different number of neutrons. Stable isotopes remain unchanged indefinitely, but unstable (radioactive) isotopes undergo spontaneous disintegration.