In Rutherford’s α-particle scattering experiment, most of the α-particles pass straight through the gold foil. This shows that
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → the nucleus is very tiny
Option (1) the positive charge is evenly distributed inside the nucleus — Incorrect. The α-particles that go straight through never come near a nucleus, so they carry no information about how the charge is arranged inside it.
Option (2) the nucleus is neutral — Incorrect. The nucleus carries the entire positive charge of the atom, Ze (79e for gold). Its Coulomb repulsion scatters the few α-particles that come close.
Option (3) the nucleus is positively charged — Incorrect. The nucleus is positive. But this is shown by the few α-particles repelled through large angles. The particles that pass straight through do not show it.
Option (4) the nucleus is very tiny — Correct. The nucleus is about \( 10^{-15} \) m to \( 10^{-14} \) m across, while the atom is about \( 10^{-10} \) m. So most of the atom is empty space. Most α-particles therefore never come near a nucleus and pass through the foil undeflected.
NCERT (2026-27):
Alpha-particle Scattering and Rutherford’s Nuclear Model of Atom – “… Rutherford’s experiments suggested the size of the nucleus to be about 10–15 m to 10–14 m. From kinetic theory, the size of an atom was known to be 10–10 m, about 10,000 to 100,000 times larger than the size of the nucleus. … Thus, most of an atom is empty space. With the atom being largely empty space, it is easy to see why most α-particles go right through a thin metal foil.”