Alpha Particles and Alpha Decay
Alpha particles are helium nuclei of nuclear origin. It carries 2 unit positive charge and its mass is about four times the mass of hydrogen atom.
Phenomenon of emission of an α particles from a nucleus is called alpha decay
Example: 92U238 →90Th234 + 2He4 + Q
Here, Q = (mX ‒ mY ‒ mHe) c2
ZXA → z ‒ 2YA ‒ 4 + 2He4 + Q
Beta Particles and Beta Decay
Beta particles are fast moving electrons of nuclear origin. A nucleus that decays spontaneously by emitting an electron or a positron is said to undergo beta decay.
In β‒ decay, an electron an electron is emitted by the nucleus.
Example: 15P32 → 16S32 + e‒ + antineutrino
In β+ decay, a positron is emitted by the nucleus.
Example: 11Na22 → e‒ + Neutrino
In beta-minus decay, a neutron transforms into a proton within the nucleus according to, n → p + e‒ + antineutrino
Whereas in beta-plus decay, a proton transforms into neutron (inside the nucleus) by, p → p + e+ + neutrino
Gamma Radiations and Gamma decay
There are energy levels in a nucleus, just like there are energy levels in atoms. When a nucleus is in an excited state, it can make a transition to a lower energy state by the emission of electromagnetic radiation. As the energy differences between levels in a nucleus are of the order of MeV, the photons emitted by the nuclei have MeV energies and are called gamma rays