Rutherford and Chadwick

Rutherford's Gold Foil Experiment00:00:01

Ernest Rutherford tested Thomson's plum pudding model using a gold foil experiment. By firing positively charged alpha particles at a thin gold sheet, he expected them to pass through easily. Instead, some deflected at large angles or bounced back, proving the existence of a dense, positively charged center called the nucleus.

Developing the Nuclear Model00:04:46

Following his discovery, Rutherford proposed a new atomic model with a small, heavy, positively charged nucleus at the center containing protons, while electrons moved in the surrounding empty space. This model was later refined because the proton mass alone did not account for the total mass of the nucleus.

Chadwick and the Discovery of Neutrons00:06:32

In 1931, James Chadwick discovered the neutron—a neutral subatomic particle located in the nucleus—by firing radiation at beryllium. This completed the nuclear model of the atom, which consists of protons and neutrons in the nucleus and electrons in the exterior space.

The Scale of the Atom00:08:35

The video concludes by illustrating the immense empty space within an atom. If the nucleus were the size of a pen cap, the nearest electron would be over 760 meters away, emphasizing that atoms are composed primarily of nothingness.