Which particle has constant charge to mass ratio for all matter?

A particle having no charge and no mass is

Figure shows tracks of three charged particles crossing a uniform electrostatic field with same velocities along horizontal. Give the sign of the three charges. Which particle has the highest charge to mass ratio?

Cathode rays have same charge to mass ratio as

If a charged particle of charge to mass ratio (q/m) = alpha centers in a magnetic field of strength B at a speed v=(2 alpha d) (B), then

Matter has no mass.

The charge to mass ratio of alpha- particles is approximately to the charge to mass ratio of protons:

J. chadwick discovered a sub atomic particle which has no charge but has mass nearly equal to that of a proton.Name the particle and give its location in an atom.