Question

Rutherford's alpha-particle scattering experiment was responsible for the discovery of:

• A. atomic nucleus
• B. electron
• C. number of proton
• D. number of neutron

Hint:

Rutherford's alpha-particle scattering experiment provided crucial evidence for the existence of the atomic nucleus. It demonstrated that the positive charge and most of the mass of an atom are concentrated in a very small region at the center, challenging the previous models of atomic structure.

Answer 1

The Correct Option is A

Step 1: Understand Rutherford's Alpha-Particle Scattering Experiment.
In 1909, Ernest Rutherford conducted an experiment where alpha particles were directed at a thin gold foil. The results of this experiment led to the discovery of the atomic nucleus. Key observations from the experiment include: 1. Most alpha particles passed straight through the foil without deflection. 2. A small fraction of alpha particles were deflected at large angles, indicating that they encountered a concentrated region of positive charge within the atom. These observations contradicted the prevailing "plum pudding" model of the atom proposed by J.J. Thomson, which suggested that the positive charge was uniformly distributed throughout the atom. Instead, Rutherford concluded that the positive charge (and most of the mass) must be concentrated in a small, dense region at the center of the atom, now known as the atomic nucleus. Step 2: Analyze Each Option.
Option (1): atomic nucleus — Correct, as Rutherford's experiment directly led to the discovery of the atomic nucleus.
Option (2): electron — Incorrect, as electrons were discovered earlier by J.J. Thomson using cathode ray experiments.
Option (3): number of proton — Incorrect, as the number of protons was not directly determined by this experiment.
Option (4): number of neutron — Incorrect, as neutrons were discovered later by James Chadwick in 1932.
Step 3: Final Answer. $$ (1) \mathbf{\text{atomic nucleus}} $$