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According to Rutherford's alpha-particle scattering experiment, where is the most mass of the atom concentrated?
In the electron cloud
In the nucleus
In the orbits
Distributed uniformly
In the nucleus
Rutherford's gold‑foil experiment showed that most of an atom’s mass is confined to a very small, dense centre called the nucleus. The surrounding electron cloud contributes only a tiny fraction of the total mass.
Rutherford's gold‑foil experiment showed that most of an atom’s mass is confined to a very small, dense centre called the nucleus. The surrounding electron cloud contributes only a tiny fraction of the total mass.
Think of a plum‑pudding model as a soft cake with raisins everywhere, whereas Rutherford’s model is like a tiny cherry (nucleus) at the centre of a large, airy soufflé (electron cloud).
Rutherford’s Nucleus Holds Mass – RNHM
dΩdσ=(4πepsilon014E2Ze2)2sin4(θ/2)1 — Rutherford differential scattering cross‑section
F=kr2Ze2 — Coulomb force between alpha particle (charge +2e) and nuclear charge Ze
When alpha particles were directed at a thin gold foil, most passed through with little deflection, but a few were scattered at large angles. This could only occur if a massive, positively charged core occupied a minute volume, exerting a strong Coulomb force on the incoming particles. The scattering distribution is described by the Rutherford formula, confirming that the mass and positive charge are concentrated in the nucleus.
~99.9% of an atom’s mass resides in the nucleus
The nucleus occupies ~10⁻⁵ of the atomic volume but contains virtually all the mass
Nuclear energy production (fission/fusion)
Particle accelerator experiments that probe nuclear structure
Standard atomic mass unit (u) is defined from carbon‑12 nucleus, illustrating that mass is essentially nuclear
Option A is wrong because electrons have negligible mass; Option C (orbits) is a historical concept without mass significance; Option D is incorrect as mass is not uniform across the atom
B is correct — The atom’s mass is concentrated in a tiny, dense nucleus at its centre.
Recall that Rutherford’s experiment disproved the plum‑pudding model; any question about where an atom’s mass lies points directly to the nucleus.
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