What is the difference between Helium3, and Helium?

Aproton is projected into a uniform electric field that points vertically upward and has magnitude e. the initial velocity of the proton has a magnitude v0 and is directed at an angle a below the horizontal. (a) find the maximum distance hmax that the proton descends vertically below its initial elevation. you can ignore gravitational forces. (b) after what horizontal distance d does the proton return to its original elevation? (c) sketch the trajectory of the proton. (d) find the numerical values of hmax and dife = 500 n> c, v0 = 4.00 * 105 m> s, anda = 30.0°.