In Rutherford's gold foil experiment the alpha particles pass through which part of the atom?
A. the nucleus
B. the proton shield
C. the valence electron shell
D. the electron cloud
D. the electron cloud
The correct answer is A. the nucleus.
To understand why the alpha particles pass through the nucleus, let me explain Rutherford's gold foil experiment briefly.
Rutherford's experiment involved firing alpha particles (which are positively charged) at a thin gold foil. According to the prevailing theory at that time, known as the Thomson model, it was believed that the atom was uniformly filled with positive charge and electrons were dispersed throughout. However, Rutherford's experiment showed something completely unexpected.
Most of the alpha particles did pass through the gold foil, but to Rutherford's surprise, a small fraction of them were scattered at large angles, and a few even bounced straight back! This observation directly contradicted the idea of a uniformly distributed positive charge.
From this experiment, Rutherford proposed a revised atomic model now known as the "nuclear model." According to this model, an atom consists of a small, dense, positively charged nucleus at the center with electrons orbiting around it.
So, in Rutherford's gold foil experiment, the alpha particles pass through the empty space within the atom, known as the electron cloud, and encounter the positively charged nucleus. Hence, the correct answer is A. the nucleus.