Which of the following was not a conclusion obtained from the gold foil-alpha particle scattering experiment?
A) An atom is mostly empty space.
B) An atom’s nucleus is positively charged.
C) An atom’s nucleus contains protons and neutrons.
D) Most of the mass of an atom is concentrated in its nucleus.
The correct answer and explanation is :
The correct answer is C) An atom’s nucleus contains protons and neutrons.
Ernest Rutherford’s gold foil experiment, conducted in the early 1900s, was pivotal in shaping our understanding of atomic structure. In this experiment, Rutherford and his team directed a beam of positively charged alpha particles at a thin sheet of gold foil. They observed that while most alpha particles passed through the foil unaffected, a small fraction were deflected at large angles, and a very few even rebounded almost directly backward. These unexpected results led to several significant conclusions:
- An atom is mostly empty space: The observation that most alpha particles traversed the foil without deflection indicated that atoms consist largely of empty space, allowing these particles to pass through unobstructed.
- An atom’s nucleus is positively charged: The deflection of some alpha particles suggested the presence of a concentrated, positively charged region within the atom. When alpha particles, which are themselves positively charged, approached this region, they experienced repulsive forces, causing their paths to alter.
- Most of the mass of an atom is concentrated in its nucleus: The fact that a few alpha particles were deflected at very large angles or rebounded indicated that the nucleus, though tiny, contains the majority of the atom’s mass, providing the necessary force to cause such significant deflections.
However, the presence of neutrons in the nucleus was not a conclusion derived from Rutherford’s gold foil experiment. Neutrons were discovered later by James Chadwick in 1932, well after Rutherford’s findings. Therefore, the statement that an atom’s nucleus contains protons and neutrons was not a conclusion obtained from the gold foil-alpha particle scattering experiment.