Question

Describe the method used by Rutherford to estimate the size of nucleus.

Short answer

Rutherford used alpha particle deflections in his gold foil experiment to estimate that the nucleus is much smaller than the atom.

Step-by-step solution

- Conducting the Gold Foil Experiment

Rutherford conducted an experiment where alpha particles were directed at a thin sheet of gold foil. He then measured the scattering of these particles.

- Observing the Deflections

Rutherford observed that most alpha particles passed through the foil with little or no deflection, while a small fraction were deflected at large angles.

- Analyzing the Results

Rutherford concluded that the large-angle deflections were caused by a concentrated positive charge within the gold atoms, which he called the nucleus.

- Calculating the Nucleus Size

Using the deflection angles and the known properties of alpha particles, Rutherford estimated the size of the nucleus to be much smaller than the size of the atom.

Key concepts

alpha particles

Alpha particles are essential to the Rutherford Gold Foil Experiment. They are positively charged particles, consisting of two protons and two neutrons. This gives them a relatively large mass and a positive charge. In Rutherford's experiment, he used a source of alpha particles and directed them at the gold foil. Due to their positive charge, alpha particles can interact with the positively charged components inside the atoms they encounter. This interaction was key to understanding the structure of the atom.

nucleus size

The size of the nucleus was a major surprise of Rutherford's Gold Foil Experiment. By observing the behavior of alpha particles after hitting the gold foil, Rutherford determined that most of an atom is empty space. Only a few alpha particles were deflected. From this, Rutherford concluded that the nucleus, the central part of the atom, must be incredibly small compared to the entire atom. This nucleus carries most of the atom's mass and positive charge. He estimated the nucleus to be about 1/100,000th of the size of the entire atom.

scattering experiment

The scattering experiment was groundbreaking. Alpha particles were fired at a thin sheet of gold foil. Most passed straight through, showing atoms are mostly empty space. However, some particles deflected at large angles or bounced back. This meant they encountered something small and dense. Rutherford used these observations to suggest the existence of a central nucleus in the atom. This experiment overturned the previous plum pudding model of the atom, which proposed that atoms were a diffuse cloud of positive charge with electrons scattered throughout.

deflection angles

Deflection angles observed in Rutherford's experiment were crucial. Most alpha particles experienced little to no deflection, indicating they passed through empty space. However, some were deflected at larger angles, and a few even bounced back. This showed that they hit the dense, positively charged nucleus. By analyzing these deflection angles, Rutherford could estimate the relative size and charge of the nucleus. Larger deflection angles indicated closer encounters with the nucleus, while particles passing through with minimal deflection confirmed the surrounding empty space.