Answer:
210 82Pb-----> 206 80Hg + 4 2 He
55 24 Cr----->55 25 Mn + 0 -1 e
76 35 Br + 0 -1 e-----> 76 34 Se
Explanation:
Alpha decay occurs with atoms having high atomic number number. As the atomic number increases, the repulsions between the protons make the nucleus unstable. A point is reached where the attractive forces in the nucleus are unable to hold the nucleons together anymore. Part of the nucleus now breaks off as an alpha particle or a helium nucleus.
Beta decay involves the transformation of a neutron to a proton, electron and neutrino. It decreases the neutron-proton ratio.
The capture of an orbital electron converts a proton into a neutron with the emission of a neutrino. The atomic number of the product nucleus decreases. Orbital electron capture increases the neutron-proton ratio.
