# Radioactivity --- **Radioactivity** is the emission of ionizing radiation or particles caused by the spontaneous disintegration of [[atom|atomic nuclei]]. ## Radioisotopes **Radioisotopes** are [[atom#Neutrons Isotopes|isotopes]] that are fundamentally unstable due to a missmatch between their number of protons and neutrons. In order to become stable, these radioisotopes are constantly shanging up their configurations to try to stabilize. Under [[atom#Protons Atomic Number|atomic number]] 20, the stable ratio is 1:1, but after that it begins to skew towards having more neutrons. The below graph shows the ratio that provides stability for a given element. Note that above [[atom#Protons Atomic Number|atomic number]] 82 there are no stable isotopes possible. ![[isotope stability.png]] ## Radioactive Decay **Radioactive decay** is the *spontaneous* breaking down of a radioisotopes nucleus in hopes that it will stabalize. This results in the releasing of [[energy]] and [[matter]] from the nucleus itself, and often end up transforming into a new element entirely. The process of changing into a new element is called **transmutation**. The radioactive decay and transmutation process will continue until a new, stable and non-radioactive element is formed. Transmutation can also be achieved artificailly. ![[radioactive decay types.png]] ### α Decay In **alpha decay**, an *alpha particle* composed of two protons and two neutrons are emitted from the nucleus. ### ß Decay In **beta decay**, a *beta particle* composed of a highly energetic electron or positron is emited from the nucleus. ### γ Decay In **gamma decay**, energy in the form of *gamma radiation* is emitted from the nucleus. Alpha and beta decay are almost always accompanied by gamma decay. Gamma rays are [[electromagnetic spectrum|electromagnetic]] waves with very high frequencies and [[energy]]. Gamma rays are identical to [[x-ray|X-rays]], except that X-rays are artificially produced and Gamma rays are naturally occurring. ## Half-Life An isotope's **half-life** is the time it takes for the radioactivity of that isotope to fall to half of it's original value. Isotopes undergo radioactive decay at a *highly predictable* property of atoms. This is how we date rocks and fossils. Uranium-238 decays into lead at a constant, relativly slow rate: it's half life is 4.5 billion years (which is also about the age of the Earth). This means uranium-238 is not very radioactive. Polonium-210 on the other hand has a half-life of 138 days, so it is very radioactive. ![[uranium-238 decay.png]] ___