In the equation 226/88 Ra--> 4/2 He+ ------, the characteristics of the missing particle are:
B) charge, 86; nucleons, 230
C) charge, 90; nucleons, 222
D) charge, 86; nucleons, 222
226/88 Ra is the particle on the left of the reaction.
It has an atomic number (number of protons) of 88.
It has a mass number, or total number of nucleons (protons and neutrons) of 226.
Since the reaction starts with an atom which is above 100, this is a radioactive decay process.
Since one of the ...
the explanation is thoroughly explained and clearly stated.