Question

Write the identity of the missing nucleus for the following nuclear decay reaction 90Th232=88Ra228+

Answer 1

Because the sums of both the top and bottom numbers (the mass number and atomic numbers) of each side must be equal, we know that the atomic number must be 2 because 88+2=90 and the mass number must be 4 so 228+4=232. Thus, because the atomic number is 2, you know this is helium so 4/2 He. This is a classic example of alpha decay.
Sorry I would but it in the proper form if I was able to do the equations but I'm on my iPad so I am unable too!