Question

Rutherford was able to carry out the first nuclear transmutation reactions by bombarding nitrogen-14 nuclei with alpha particles. In the famous experiment on scattering of alpha particles by gold foil (Section 2.2), however, a nuclear transmutation reaction did not occur. What is the difference between the two experiments? What would one need to do to carry out a successful nuclear transmutation reaction involving gold nuclei and alpha particles?

Short answer

The difference between Rutherford's nitrogen-14 transmutation reaction and the gold foil experiment is the energy of alpha particles and the nuclei involved. In the nitrogen-14 transmutation reaction, alpha particles had enough energy to overcome the electrostatic repulsion between them and the nitrogen-14 nuclei, resulting in a successful nuclear transmutation. However, in the gold foil experiment, alpha particles did not have enough energy to overcome the electrostatic repulsion with gold nuclei, thus no transmutation occurred. To achieve nuclear transmutation involving gold nuclei and alpha particles, the energy of alpha particles must be increased sufficiently to overcome the electrostatic repulsion, and the reaction should be carried out under controlled conditions with appropriate detection equipment.

Step-by-step solution

Understanding the Nitrogen-14 Transmutation Reaction

Rutherford bombarded nitrogen-14 nuclei with alpha particles and observed the release of a proton. This transmutation reaction can be represented by the equation: \[ {}^{14}_7N + {}^4_2He \rightarrow {}^{17}_8O + {}^1_1H \] In this reaction, nitrogen-14 nuclei absorbed alpha particles and transformed into oxygen-17 nuclei, releasing a proton. This is a successful nuclear transmutation process.

Understanding the Gold Foil Experiment

In the gold foil experiment, Rutherford used a beam of alpha particles to study the scattering by gold nuclei. Most of the alpha particles passed through the gold foil with minimal or zero deflection, while a few alpha particles experienced large deflections. A nuclear transmutation did not occur in this experiment as the alpha particles did not have enough energy to overcome the electrostatic repulsion between them and the gold nuclei.

Identifying the Difference Between the Two Experiments

The key difference between the nitrogen-14 transmutation reaction and the gold foil experiment is the energy of the alpha particles and the nuclei involved: 1. In the nitrogen-14 transmutation reaction, the alpha particles had enough energy to overcome the electrostatic repulsion between them and the nitrogen-14 nuclei. This allowed the alpha particles to be absorbed by the nitrogen-14 nuclei, resulting in a transmutation reaction. 2. In the gold foil experiment, the alpha particles did not have enough energy to overcome the electrostatic repulsion between them and the gold nuclei. As a result, there was no absorption of the alpha particles by the gold nuclei, and no transmutation reaction occurred.

Carrying Out a Successful Nuclear Transmutation Reaction Involving Gold Nuclei and Alpha Particles

To carry out a successful nuclear transmutation reaction involving gold nuclei and alpha particles, the energy of the alpha particles must be increased enough to overcome the electrostatic repulsion between them and the gold nuclei. By providing the alpha particles with sufficient energy, the alpha particles can be absorbed by the gold nuclei, yielding a transmutation reaction. Moreover, the reaction should be carried out under controlled conditions and with the appropriate detection equipment to observe the results.

Key concepts

Alpha Particles

Alpha particles, often represented by the Greek letter \( \alpha \), are positively charged particles that consist of two protons and two neutrons. These particles are identical to the nucleus of a helium atom. Due to their positive charge and relatively heavy mass, alpha particles have a strong tendency to interact with matter.
Alpha particles play a pivotal role in nuclear reactions, particularly in nuclear transmutation. Their ability to induce changes in the nucleus of another atom makes them valuable tools for investigating atomic structure.
When alpha particles are directed at a material, they may cause transmutations, like in the transformation of nitrogen-14 into oxygen-17 as observed in Rutherford's groundbreaking experiments. However, their success in penetrating other nuclei is highly dependent on the energy of the alpha particles and the nature of the target atom.

Rutherford Experiment

The Rutherford Experiment was a landmark study in nuclear physics conducted by Ernest Rutherford. By directing a beam of alpha particles at a thin foil, Rutherford made comprehensive observations about how these particles scattered. This experiment was crucial in advancing our understanding of atomic structure.
Prior to Rutherford's work, the prevalent model of the atom was J.J. Thomson’s "plum pudding model." However, the Rutherford Experiment revealed inconsistencies with this model, showing that most of an atom’s mass is concentrated in a dense central nucleus. The deflection patterns of alpha particles provided evidence that atoms have a small, dense nucleus surrounded by vast empty space, reshaping concepts of atomic structure. This experiment laid the foundation for the modern nuclear model of the atom.

Gold Foil Experiment

The Gold Foil Experiment, also known as the Geiger-Marsden experiment, was a crucial part of Rutherford's research. In this experiment, a thin sheet of gold foil was bombarded with a stream of alpha particles. Observations revealed that while most passed through the foil without deflection, a small fraction experienced large deflections.
This surprising outcome indicated that the positive charge in an atom is concentrated in a very small area: the nucleus. The gold foil experiment fundamentally shifted the atomic models of the time and revealed the presence of the atomic nucleus. It demonstrated how even a thin foil can provide significant insights into the internal structure of atoms through scattering patterns and deflections of alpha particles.

Electrostatic Repulsion

Electrostatic repulsion is a key concept in understanding how atomic particles interact. It refers to the force that pushes like-charged particles apart. In the context of nuclear and particle physics, this force is crucial when dealing with positively charged entities such as alpha particles.
When alpha particles approach a nucleus, such as gold, they experience a significant electrostatic repulsion. This is due to the positive charge of both the alpha particles and the gold nuclei. To overcome this repulsion and achieve nuclear transmutation, the incoming particles must possess higher energy levels.
The Gold Foil Experiment clearly illustrated the effects of electrostatic repulsion. Only those alpha particles with sufficient energy could come near the gold nucleus, while others were deflected. Understanding this repulsion is vital for predicting and controlling nuclear reactions.