DexBeta decay is accompanied by the emission of an electron (or positron)or by capture of an electron from

dexBeta decay is accompanied by the emission of an
electron (or positron)or by capture of an electron from
the electron shell of an atom.
Simultaneously the initial nucleus units a neutrino or
an antineutrino.
The half-lives of β-active nucler is in the range
10^-2sec18years (16)
There are three kinds of β-decay:
-β^- -decay;
-β⁺ -decay;
-electron capture.
In β^—decay the initial nucleus units an electron and an
antineutrino (ν_e). The mass number of nucler do not
change in β^- -decay. The atomic number of the final
nucleus is one unit more than the atomic number of the
initial nucleus
→ + e^- + ν_e (17)
The simple β-decay is the decay of a neutron
n→p+e^- +ν_e (18)
The following energy is released(liberated)in β^- -decay

= [M( )-M( -m_e]c² (19)