CBSE Class 12-science Answered

Alpha particles are composite particles consisting of two protons and two neutrons tightly bound together . They are emitted from the nucleus of some radionuclides during a form of radioactive decay, called alpha-decay. An alpha-particle is identical to the nucleus of a normal (atomic mass 4) helium atom or a doubly ionised helium atom.

Alpha particles are relatively slow and heavy compared with other forms of nuclear radiation. The particles travels at 5 to 7 percent of the speed of light or 20,000,000 metres per second and has a mass approximately equivalent to 4 protons.