Compare with isotope and polymorph . Some elements occur in several distinct forms called allotropes. Allotropes have different chemical and physical properties. For example, graphite and diamond are allotropes of carbon. A particle that is commonly ejected from radioactive nuclei, consisting of two protons and two neutrons.
Alpha particles are helium nuclei.
A stream of alpha particles . Alpha rays rapidly dissipate their energy as they pass through materials, and are far less penetrating than beta particles and gamma rays . Compare with cation . An anion is a negatively charged ion. Nonmetals typically form anions.