Definition for Alpha particle
From Biology Forums Dictionary
Alpha particles consist of two protons and two neutrons bound together into a particle identical to a helium nucleus. They are generally produced in the process of alpha decay, but may also be produced in other ways. Alpha particles are named after the first letter in the Greek alphabet, α. The symbol for the alpha particle is α or α2+. If the ion gains electrons from its environment, the alpha particle can be written as a normal (electrically neutral) helium atom 42He.