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I can tell you it's not a relativistic particle, as its rest mass (0.511MeV) is much larger than 1% of the kinetic energy. With regards to the radius of the circle, perhaps it would have something to do with F = qv x B, where v and B are the vectors of velocity and magnetic field respectively whilst v x B is the cross product, but you can just assume their magnitudes and make it F = qvB.

An alpha particle has a mass of four (2 protons and 2 neutrons) consequently 6 would be an entire of 24 mass units. consequently your mass would be 208. A beta particle is an electron or positron and for our purposes has no mass, yet this could influence the atomic selection that's comparable to the style of electrons. So your atomic selection would be 86. consequently your good daughter could have an atomic style of 86 and a mass style of 208. Cheers, Andrew