(a) A radioactive transformation in which an αparticle is emitted is called α-decay. In an α-decay, the atomic number of the nucleus decreases by 2 and the mass number decreases by 4.
(b) A radioactive transformation in which a βparticle is emitted is called β-decay. In a β -decay, the atomic number of the nucleus increases by 1 and the mass number remains unchanged.
where \(\bar{v}\) is the neutrino emitted to conserve the momentum, energy and spin.
Q = [ mu - mTh - m\(_\alpha\)]c2
In a β+ -decay, the atomic number of the nucleus decreases by 1 and the mass number remains unchanged.
where ve is the neutrino emitted to conserve the momentum, energy and spin.
Q = [mp - msi - me}c2
[Note : The term fi particle refers to the electron (or positron) emitted by a nucleus.]
A given nucleus does not emit α and βparticles simultaneously. However, on emission of α or β-particles, most nuclei are left in an excited state. A nucleus in an excited state emits a γ-ray photon in a transition to the lower energy state. Hence, α and βparticle emissions are often accompanied by γ-rays.