Rutherford's Alpha-Particle Scattering Conclusions

Steps:

• Alpha particles (helium nuclei) were fired at thin gold foil.
• Most particles passed straight through, indicating atoms are mostly empty space.
• A few particles deflected at large angles, showing a concentrated positive mass in the atom.
• This led to the nuclear model where mass is centralized in a tiny nucleus.

Why C is correct:

• Large-angle deflections occur because alpha particles bounce off the dense, massive nucleus, per conservation of momentum, proving the nucleus holds most atomic mass.

Why the others are wrong:

• A: Charge equality known from electrolysis and Thomson's experiments, not scattering.
• B: Electron-proton mass ratio from J.J. Thomson's cathode ray work, predating scattering.
• D: Neutrons discovered later (1932) by Chadwick; scattering only revealed protons in nucleus.

Final answer: C