The state of matter depends upon how close the individual particles are together
The magnetic force experienced by the proton is given by

where q is the proton charge, v its velocity, B the magnitude of the magnetic field and

the angle between the direction of v and B. Since the proton moves perpendicularly to the magnetic field, this angle is 90 degrees, so

and we can ignore it in the formula.
For Netwon's second law, the force is also equal to the proton mass times its acceleration:

So we have

from which we can find the magnitude of the field:
Steel paper clip because it can be moved by the magnet and it is lighter than the iron nail
The object will not be able to accelerate perpendicular to direction of motion