Alpha particles are sometimes referred to as alpha rays or alpha radiation. Alpha particles are positively charged particles that are emitted during the radioactive decay of different types of radioactive materials. The mass of an alpha particle is made up of two neutrons and two protons; therefore, an alpha particle nucleus is quite similar to a helium-4 nucleus. Alpha particle is indicated by a symbol which is a Greek alphabet α.
Alpha particles have a large mass as they are made up of 4 nucleons and a mass number of 4. They carry two protons; therefore, they are charged. The relative charge of an alpha particle is +2. The range of ionizing radiation of alpha particles is relatively short. These particles can travel only a few centimeters in the air and cannot penetrate more than a few millimeters of paper. The alpha particles react with different types of atoms along their path, giving up energy rapidly and having a short range. Alpha particles have about 5-8 cm of range in the air. It is easily stopped by air.
A radioactive element in the periodic table, radium-222, is a radioactive element that decays to become the element radon by emitting alpha particles. The element radon is a radioactive gas that decays further, giving up alpha particles. When a radioactive element decays, the element's mass number decreases by four, and the atomic number is reduced by 2. This happens due to the emission of alpha particles.