Question

In 1911, the physicist Ernest Rutherford discovered that atoms have a tiny, dense nucleus by shooting positively charged particles at a very thin gold foil. What was the key physical property which led Rutherford to use gold?
A) Electrically conducting
B) Highly malleable
C) Shiny
D) Non-reactive

Answer 1

To successfully conduct the experiment, Rutherford required that the gold foil be as thin as a thousand atoms thickness. Other physical properties were of no relevance to the experiment he was conducting.

Complete step by step solution:
Before 1911, it was thought that the atom was like a plum pudding or like watermelon. This was Thomson's model of an atom. In this model, Thomson had proposed that the atom had negatively charged electrons embedded in the positive charge of the atom like the plum in the pudding. In this model, the positive and negative charge of the atom was assumed to be distributed evenly throughout the atom.

In 1911, Ernest Rutherford performed the gold foil experiment in which he obtained thought provoking results. He found that when he fired alpha particles onto the gold foil, many of the alpha particles passed through the gold foil undeflected. Few of the alpha particles were deviated by some angle and very rare alpha particles had a 180$^\circ$ deviation. This suggested that most of the volume of the atom is vacant, and there is a tiny, dense nucleus where all the positive charge of the atom is concentrated. For this experiment to be successful, he needed that the material he uses is extremely thin so that the results obtained could be accurately used for single atoms. If the material used for the experiment would have been too thick, there would have been a lot of layers of atoms with which the beam of alpha particles would have interacted while moving in a straight line, so the results could have not been used to determine the structure of the atom. Thus, the most important property for Rutherford while choosing the material for the experiment was its malleability, which is the ability of being beaten into thin sheets. The more malleable the material, the thinner sheets the material can be beaten into. Gold is highly malleable and that is why Rutherford chose to use extremely thin gold foil for his experiment. All the other properties were not of much concern to him.

Therefore, the most important property of gold because of which Rutherford used it in his experiment is its high malleability.

Hence, the correct answer for this question is option B.

Note: The important conclusions Rutherford obtained from this experiment are listed below:
-Most of the space inside the atom is empty because most of the α-particles passed through the gold foil without getting deflected.
-Very few particles were deflected from their path, indicating that the positive charge of the atom occupies very little space.
-A very small fraction of α-particles were deflected by very large angles, indicating that all the positive charge and mass of the gold atom were concentrated in a very small volume within the atom.