Use Rutherford's gold-foil experiment to answer each of the following:
b. How did the results differ from what he expected?

Verified step by step guidance

1. Rutherford's gold-foil experiment involved directing a beam of alpha particles (positively charged particles) at a very thin sheet of gold foil to study the structure of the atom.
2. Based on the prevailing plum pudding model of the atom, Rutherford expected the alpha particles to pass through the gold foil with only slight deflections, as the positive charge and mass were thought to be evenly distributed throughout the atom.
3. However, the experimental results showed that while most alpha particles passed through the foil as expected, a small fraction were deflected at large angles, and some even bounced back toward the source.
4. This unexpected observation indicated that the positive charge and most of the mass of the atom were concentrated in a very small, dense region, which Rutherford called the nucleus.
5. The results of the experiment led to the rejection of the plum pudding model and the development of the nuclear model of the atom, where electrons orbit a dense, positively charged nucleus.

Key Concepts

Rutherford's Gold-Foil Experiment

Rutherford's gold-foil experiment, conducted in 1909, involved firing alpha particles at a thin sheet of gold foil. The experiment aimed to probe the structure of the atom, which was believed to be a 'plum pudding' model with positive and negative charges distributed evenly. Instead, most alpha particles passed through, while a small fraction were deflected at large angles, leading to the conclusion that atoms have a dense, positively charged nucleus.

Expectations vs. Results

Rutherford expected that the alpha particles would pass through the gold foil with minimal deflection, consistent with the prevailing atomic model of the time. However, the unexpected large-angle deflections indicated that a significant portion of the atom's mass and positive charge was concentrated in a small volume, contradicting the earlier model and suggesting a new nuclear structure of the atom.

Nuclear Model of the Atom

The nuclear model of the atom, proposed by Rutherford after his experiment, posits that atoms consist of a small, dense nucleus containing protons and neutrons, surrounded by electrons in a relatively large space. This model replaced the earlier 'plum pudding' model and laid the groundwork for modern atomic theory, fundamentally changing our understanding of atomic structure and behavior.