Which of Rutherford's experimental observations led him to conclude that the positive charge of an atom is concentrated in a very small region?
Show answer & explanation
Correct answer: B
Explanation
Answer: A very small fraction of α-particles rebounded almost backwards.
Explanation: In Rutherford’s gold foil experiment, most α-particles passed straight through the foil, showing that most of the atom is empty space. However, a very small fraction of α-particles were deflected at very large angles, and some even rebounded nearly backward. This rare but significant observation indicated that a strong positive charge and most of the mass are concentrated in a tiny central region called the nucleus.
Additional Key Facts:
Rutherford’s experiment used a thin gold foil and α-particles.
About 99% of particles passed undeflected.
Large-angle deflections were extremely rare but crucial.
Led to the discovery of the nuclear model of the atom.
The nucleus is positively charged and very small compared to the atom.
Potential Exam-Oriented Questions & Answers:
Question: What caused the deflection of α-particles?
Answer: Repulsion by the positively charged nucleus.
Question: Who discovered the nucleus of an atom?
Answer: Ernest Rutherford.