Which one of the following findings is NOT observed in Rutherford's Nuclear Model of Atom?
- (a)There is a neutral centre in an atom called nucleus
- (b)Nearly all the mass of an atom resides in the nucleus
- (c)The electrons revolve around the nucleus in a circular path
- (d)The size of a nucleus is very small as compared to the size of atom
Correct — A, the 'neutral centre'. Rutherford's alpha-particle scattering experiment showed the nucleus is positively charged — it repelled the positive alpha particles — not neutral. So calling the nucleus a 'neutral centre' is NOT a finding of his model, which makes (a) the odd one out.
- (b)Nearly all the mass of an atom resides in the nucleus — This is a genuine Rutherford finding: almost all the atom's mass sits in the tiny nucleus, since only a few alpha particles were strongly deflected.
- (c)The electrons revolve around the nucleus in a circular path — This is part of Rutherford's model: electrons revolve around the nucleus in circular paths, much like planets around the Sun.
- (d)The size of a nucleus is very small as compared to the size of atom — This is correct too: the nucleus is extremely small compared with the whole atom, which is mostly empty space.
In the gold-foil experiment Rutherford fired alpha particles at thin foil; most passed straight through and a few deflected sharply. He concluded the atom has a tiny, dense, positively charged nucleus with electrons revolving around it in mostly empty space.
Options b, c and d are textbook Rutherford conclusions; the trap calls the nucleus 'neutral', which contradicts the very experiment in which a positive nucleus repelled positive alpha particles.
- Rutherford's nucleus is positively charged, tiny and holds nearly all the atom's mass.
- Electrons revolve around the nucleus, and most of the atom is empty space.
- The model could not explain why orbiting electrons do not lose energy and collapse — Bohr fixed this in 1913.
- The gold-foil (alpha-scattering) experiment is the basis of the nuclear model.
- Calling the nucleus 'neutral' — it is positively charged.
- Confusing Rutherford's model with Bohr's quantised, stable orbits.
A 'which is NOT a finding' item that slips a false property (a neutral nucleus) in among genuine Rutherford conclusions.
No directly related past PYQ was found.
- practice — not a real PYQ
In Rutherford's gold-foil experiment, most alpha particles passed straight through the foil because
- (a)The atom is mostly empty space
- (b)Alpha particles are neutral
- (c)The nucleus is negatively charged
- (d)Electrons deflected them
Answer(a) The atom is mostly empty space.
- practice — not a real PYQ
The main drawback of Rutherford's atomic model, later resolved by Bohr, was that it could not explain
- (a)The stability of the atom
- (b)The mass of the nucleus
- (c)The existence of electrons
- (d)The size of the atom
Answer(a) The stability of the atom — why revolving electrons do not spiral into the nucleus.