Some typical examples of alpha decays are:
238U92 ® 234U90 + 4He2
208Po84 ® 204Pb82 + 4He2
Many isotopes of elements with atomic number greater than 83 are alpha emitters. Some rare earth elements (114Nd, 146Sm, ... 174Hf) and some light elements (8Li, 9Li etc) also emit alpha particles.
When a nuclide MPZ emits an electron, we may consider one of the neutron in the nucleus being converted to a proton. For example,
40Ca19 ® 40Ca20 + e- + v*
50V23 ® 50Cr24 + e- + v*
87Rb37 ® 87Sr38 + e- + v*
21Na11 ® 21Ne10 + e+ + v
30P15 ® 30Si14 + e+ + v
34Cl17 ® 34S16 + e+ + v
116Sb51 ® 116Sn50 + e+ + v
48V23 + e- ® 48Ti22 + v (+ X-ray) (50%)
40K19 + e- ® 40Ar18 + v (+ X-ray)
65Zn30 + e- ® 65Cui29 + v (+ X-ray)
7Be4 + e- ® 7Li3 + v (+ X-ray)
After alpha or beta emission, some daughter nuclei have excess energy, and they become stable after emission of gamma photons. Thus, gamma rays are emitted almost at the same time beta or alpha rays are emitted.
24Na11 ® 24Mg12 + e- + v* + g
Nuclei not releasing the excess energy immediately are called isomers, which are represented by a superscript m following the mass number. These isomers emit gamma rays.
99mTc ® 99Tc + g
60mNi28 + e- + v*
60mNi ® 60Ni + g
This two-step process is in competition with the immediate release of gamma rays.
An isomer may also undergo an internal conversion to release its energy. In this process, an electron from the inner atomic orbital is ejected, and the electron so ejected may be as energetic as beta particles. This is another mode of gamma decay.
As an example, the fission 256Fm may be represented by
The fission process splits the nucleus into two large fragments and some neutrons.
These processes can be represented as b+a, and b-a, respectively. Another example of b+a, is,