An alpha particle is made up of two protons and two neutrons. An alpha particle is common in the field of nuclear physics because it is one of the three particles emitted during radioactive decay. The three particles emitted during radioactive decay are alpha, beta and gamma.
Alpha particles became well-known thanks to Ernest Rutherford's use of alpha particles as projectiles with gold foil serving as the target. This experiment led to the discovery of the atom's structure. Rutherford concluded that atoms had dense, positively charged cores with lighter, negatively charged electrons orbiting them. Most of the alpha particles passed through the gold foil with ease. However, in rare cases, the particles collided with or came close to the nucleus and were deflected at wide angles. This led to Rutherford's conclusion that the core of an atom contained a minuscule and extremely dense nucleus.