Question 1

What are the main observations of Rutherford's alpha-particle scattering experiment?

Accepted Answer

Most alpha particles passed through the thin gold foil with little or no deflection. A small fraction were deflected through small angles, and a very small fraction were scattered through large angles or back toward the source.

Question 2

Why did most alpha particles passing through gold foil show that the atom is mostly empty space?

Accepted Answer

Most particles passed through with almost no deflection, showing that they encountered very little concentrated positive charge or mass. A diffuse positive charge spread throughout the atom would mostly produce small deflections, but it would not explain the rare large-angle or backward scattering events.

Question 3

What did rare large-angle scattering reveal about the nucleus?

Accepted Answer

It revealed that nearly all the atom's positive charge and mass must be concentrated in an extremely small central region. The positive alpha particle approaching close to this nucleus experienced a strong electrostatic repulsion and could scatter through a large angle.

Question 4

How much larger is an atom than its nucleus?

Accepted Answer

Atomic size is of the order of 10^-10 m, while nuclear size is of the order of 10^-15 m. Thus, the nucleus is approximately 100,000 times smaller in linear scale than the whole atom.

Question 5

Why is Rutherford's model considered incomplete?

Accepted Answer

Rutherford's nuclear model explains empty space, nuclear concentration and large-angle alpha scattering. It does not explain atomic stability or the arrangement and energies of electrons in a way that accounts for atomic spectra; the Bohr model addresses these limitations.

Alpha-Particle Scattering and Rutherford's Nuclear Atom

About this lab

Practice