Rutherford's Gold Foil Experiment

Rutherford performed an experiment to determine the structure of atom in 1911. He bombarded a very thin gold foil with alpha particles from radioactive uranium.
A photo graphic plate was placed behind the foil to observe the extent of scattering
of alpha particles which deflected at different angles. Very few of them (One out of every 4000 particles) were bounced back.

Following conclusion were made about the structure of atom from the experiment.

The positive charge and almost the whole mass of the atom is concentrated in the centre of the atom called nucleus which caused the particles to bounce back. Most of the space (volume) occupied by an atom is empty as most of the particles pass through the foil undeflected.

Rutherfordium's Atomic Model:

According to Rutherford, an atom consisted of two parts:

• Nucleus:

Protons and neutrons are found inside nucleus. Protons are positively charged so the nucleus has positive charge. The weight of the atom is also due to protons and neutrons so the whole mass of the atom is also concentrated in the nucleus.

• Extra Nuclear Part:

The electrons revolve round the nucleus in the extra nuclear part in various orbits.
The orbits are also called shells or energy levels.

Defects in Rutherfordium's Atomic Model:

• If the electrons emit energy continuously,they should form a continuous spectrum but actually a line spectrum is obtained.
  

• According to the classical electromagnetic theory, the revolving electrons will lose energy continuously. Therefore, the orbit of the electrons will become smaller and smaller until the electrons fall into the nucleus.