What is Radioactive decay?
[[File:Plutonium pellet.jpg|thumb|[[Plutonium]] pellet glowing red hot due to heat from radioactive decay]] [[File:Radioactive.svg|thumb|right|150px|The [[Hazard symbol#Radioactive sign|trefoil symbol]] is used to indicate radioactive material.<!-- The [[Unicode]] encoding of this symbol is U+2622 ({{unicode|☢}}) -->]] '''Radioactive decay''' happens to some [[chemical elements]]. Most [[chemical element]]s are stable. Stable elements are made up of [[Atom|atoms]] that stay the same. Even in a [[chemical reaction]], the atoms themselves do not ever change. ==Discovery== In the 19th century, [[Henri Becquerel]] discovered that some chemical elements have atoms that change over time. In 1898, [[Marie Curie|Marie]] and [[Pierre Curie]] called this phenomenon radioactive decay.<ref>{{cite journal|author=Pierre Curie, Marie Curie, G. Bémont|title=Sur une nouvelle substance fortement radio-active contenue dans la pechblende|url=https://archive.org/stream/surunesubstancen127curi#page/n9/mode/2up|journal=Comptes rendus hebdomadaires des séances de l'Académie des sciences|issue=127|pages=1215–1217|year=1898|language=French}}</ref> Becquerel and the Curies were awarded the [[Nobel Prize in Physics]] for this discovery, in 1903. ==Example== Most [[carbon]] atoms have six [[Proton|protons]] and six [[Neutron|neutrons]] in their [[Atomic nucleus|nucleus]]. This carbon is called carbon-12s (six protons + six neutrons = 12). Its [[atomic weight]] is 12. If a carbon atom has two more neutrons it is [[carbon-14]]. Carbon-14 acts chemically like other carbon, because the six protons and six electrons are what govern its [[Chemical property|chemical properties]].{{cn|date=January 2025}} In fact, carbon-14 exists in all living things; all plants and animals contain carbon-14. However, carbon-14 is [[radioactive]]. It decays by [[beta decay]] to become [[nitrogen]]-14. Carbon-14, in the small amounts found about us in nature, is harmless. In [[archaeology]], this kind of carbon is used to determine the age of wood and other fo