Alpha particle

Alpha particles (named after and denoted by the first letter in the Greek alphabet, α) consist of two protons and two neutrons bound together into a particle identical to a helium nucleus; hence, it can be written as He2+ or 42He. They are a highly ionizing form of particle radiation, and have low penetration. The alpha particle mass is 6.644656×10-27 kg, which is equivalent to the energy of 3.72738 G eV. The charge of an alpha particle is equal to +2e, where e is the magnitude of charge on an electron, e=1.602176462x10-19C.