Which one of the following conclusions could not be derived from Rutherford's α-particle scattering experiment?
- A.Most of the space in the atom is empty.
- B.The radius of the atom is about 10⁵ times the radius of the nucleus.
- C.Electrons move in a circular path of fixed energy called orbits.
- D.Nearly all the mass of the atom resides in the nucleus.
Correct answer
Explanation
The correct answer is C, Electrons move in a circular path of fixed energy called orbits.. Orbits of fixed energy were proposed by Niels Bohr in 1913; Rutherford's experiment said nothing about the energy of electrons.
In 1911 Rutherford's team fired alpha particles at a thin gold foil. Most passed straight through, a few were deflected, and about one in many thousands bounced back. From this Rutherford concluded that the atom is mostly empty space, that its positive charge and nearly all its mass are packed into a tiny central nucleus, and that the nucleus is about 10⁵ times smaller than the atom. His model could not explain why orbiting electrons do not lose energy and fall into the nucleus; Bohr answered that with stationary orbits.
A is wrong as a choice because empty space was drawn directly from most particles passing through.
B is wrong as a choice because the size of the nucleus was estimated from the scattering.
D is wrong as a choice because the rebounding particles showed that mass is concentrated in the nucleus.
Exam tip: Rutherford, gold foil, nucleus (1911); Bohr, fixed-energy orbits (1913).
Practice Questions
View allWhich one of the following is the purest form of Carbon ?
- A.Charcoal
- B.Coke
- C.Fullerene
- D.Carbon black
Show answer
Fullerenes are made of carbon atoms alone, with no surface to trap other substances, so they are counted as the purest form of carbon.
Read the full explanation →A planet has a mass M₁ and radius R₁. The value of acceleration due to gravity on its surface is g₁. There is another planet 2, whose mass and radius both are two times that of the first planet. Which one of the following is the acceleration due to gravity on the surface of planet 2?
- A.g₁
- B.2g₁
- C.g₁/2
- D.g₁/4
Show answer
Surface gravity is g = GM/R², so doubling the mass doubles g while doubling the radius divides it by four, leaving g₁ × 2/4 = g₁/2.
Read the full explanation →Which one of the following is the major constituent of biogas ?
- A.Carbon dioxide
- B.Nitrous oxide
- C.Methane
- D.Oxygen
Show answer
Methane makes up the largest share of biogas, usually about 55 to 75 per cent, and it is the gas that burns.
Read the full explanation →A lemon kept in water in a glass tumbler appears to be larger than its actual size. It is because of
- A.reflection of light
- B.scattering of light
- C.refraction of light
- D.polarization of light
Show answer
The lemon looks bigger because light from it bends as it passes from water through the curved glass into air.
Read the full explanation →Which one of the following is the mechanism of action of oral contraceptive pills?
- A.They kill the egg.
- B.They kill the sperm.
- C.They kill the zygote.
- D.They inhibit the release of egg.
Show answer
. Oral contraceptive pills prevent pregnancy mainly by stopping the ovary from releasing an egg.
Read the full explanation →