Which is a conclusion about the atom’s structure from Rutherford’s gold foil-alpha particle experiments?
A) The electrons occupy most of the total volume of an atom
B) The mass of an atom is distributed uniformly throughout the atom.
C) All alpha particles are affected the same way by the atoms in the gold foil.
D) The positive charge of the atom is uniformly distributed throughout the atom.
The correct answer and explanation is :
The correct answer is A) The electrons occupy most of the total volume of an atom.
Explanation:
Rutherford’s gold foil experiment, conducted in 1909, was a groundbreaking experiment that led to significant advancements in our understanding of the atomic structure. Before this experiment, scientists generally believed in the “plum pudding” model proposed by J.J. Thomson, which suggested that atoms were composed of a diffuse, uniform distribution of positive charge with electrons embedded throughout, like raisins in a plum pudding.
Rutherford and his colleagues fired a stream of alpha particles (helium nuclei) at a thin sheet of gold foil. Most of the particles passed through the foil with little to no deflection. However, some particles were deflected at large angles, and a very small fraction even bounced back toward the source. This unexpected result led Rutherford to conclude that the atom must have a small, dense, positively charged center, which he called the nucleus, and that the rest of the atom consisted of largely empty space.
From this, he derived the following conclusions about the atom’s structure:
- The nucleus is small but contains most of the atom’s mass and positive charge. The fact that most alpha particles passed through the foil without deflection suggested that atoms are mostly empty space, and only a small, dense nucleus at the center could deflect the alpha particles.
- Electrons occupy most of the atom’s volume. Since most of the atom is empty space, the electrons must be located far from the nucleus, occupying a large part of the atom’s volume, while the nucleus is tiny in comparison.
This experiment overturned the “plum pudding” model and led to the development of the nuclear model of the atom, where the nucleus is at the center, and electrons orbit around it in the surrounding space.
Why the other options are incorrect:
- B) The mass of the atom is concentrated in the nucleus, not uniformly distributed.
- C) The deflections of alpha particles varied, with some being scattered at large angles, showing that the atomic structure was not uniform.
- D) The positive charge is concentrated in the nucleus, not uniformly distributed.
