Rutherford_Geiger_and_Marsden

The Rutherford Experiment: Discovery of the Nucleus

Hans Geiger

Ernest Marsden

Rutherford's Planetary Model

Rutherford was a scientist from New Zealand who, in 1910, discovered the nucleus of the atom in his scattering alpha particles experiment with the help from Hans Geiger and Ernest Marsden. Hans Geiger made equipment to count alpha particles and later invented the Gieger counter. Ernest Marsden was a student of Rutherford at the time of his historic experiment.

This is a video describing Rutherford's experiment.

Ernest Rutherford, Hans Geiger, and Ernest Marsden

It was quite the most incredible event that ever happened to me in my life. It was almost as incredible as if you had fired a 15-inch shell at a piece of tissue paper and it came back and hit you.

The discovery of the atom's nucleus came as a result of an experiment performed by Ernest Rutherford and some of his fellow scientists, Hans Geiger and Ernest Marsden. Rutherford fired positively charged alpha particles at a thin sheet of gold foil (this sheet was only a few atoms thick). They expected the alpha particles to pass through with little deflection or loss of energy. This hypothesis was based on Thompson's plum pudding model which suggests that an atom is a positive liquid-filled sphere with negative electrons suspended in it, The majority of the alpha particles passed straight through the gold, however, several had a large deflection The most surprising was that one alpha particle in every eight thousand bounced straight back. After two years of deep thinking, Rutherford, Hans, and Geiger concluded that an atom is made up of a sphere with a positively charged nucleus in the center with negatively charged electrons traveling around the outside. The positive nucleus deflected positive alpha particles in the experiment. Years later after more experiments, Rutherford discovered that the nucleus is actually made up of positively charged protons and neutral neutrons. By using his Scattering Formula, Rutherford could calculate the number of positive charges in the nucleus. From there he found that the the number of positive charges is equal to the atomic number.