Question

The correct order of increasing number of alpha particles passing undeflected through the foils of Au, Ag, Cu and Al of 1000 atoms thickness each in a simulated alpha particle scattering experiment of Rutherford would be:
(A) Au < Ag < Cu < Al
(B) Al < Cu < Ag < Au
(C) Au < Cu < Al < Ag
(D) Ag < Cu < Al < Au

Answer 1

Hint: Rutherford's scattering experiment is used to detect the volume occupied by subatomic particles, mainly nucleus. So, the atom having less effective nuclear charge indicates that the volume of the atom is more and hence more particles will go undeflected. On the other hand, the atom having greater nuclear charge will have lesser alpha particles go undeflected.

Complete step-by-step answer:
The Rutherford model was devised by the New Zealand-born scientist Ernest Rutherford to describe an atom.
The new model for the atom, which was based on experimental results, contained new features of a relatively high central positive charge present in a very small volume in comparison to the complete volume of the atom. This region came to be known as nucleus.
Rutherford's gold foil experiment was used to determine the nuclear charge of the respective atom by passing a beam of doubly charged helium ions or rather alpha particles.
As the atomic number increases, the deflection as well will start increasing due to increasing nuclear charge. Keeping this in mind we can conclude that:
The correct order of increasing number of alpha particles passing undeflected is,
Au < Ag < Cu < Al
Therefore, the correct answer is option (A).

Note: Rutherford model although proves useful, had its own share of drawbacks. Some are mentioned below:
- The orbital revolution of the electron is not expected to be stable,
- Any particle in a circular orbit would undergo an acceleration and the charged particles would radiate energy
- The revolving electron would lose energy and finally fall into the nucleus.