Question

State the three key observations and their corresponding conclusions of the alpha particle scattering experiment done by Rutherford and his team.

Answer 1

Experiment

• Rutherford had an alpha particle emitter where, alpha particles are doubly charged helium with mass number 4.
• He took a very thin gold foil about 1000 atoms thick. He selected gold metal being highly malleable (i.e, can be made into very thin sheets).
• He placed a detector to observe the deflection of alpha particles after colliding with the gold foil.

Observations

1. Most of the alpha particles passed straight through the gold foil.
2. Some of the alpha particles were deflected by small angles.
3. Very small amount of alpha particles rebounded.

Conclusions

1. Most of the space in an atom is empty.
2. Atom contains some positively charged particles but they occupy a small volume of space since only a few alpha particles were deflected from their path.
3. A very few alpha particles were rebounded means mass of the atom and positive charge was concentrated at a small volume in an atom.

Rutherford model of atom

• The nucleus is at the centre and it contains most of the mass and all the positive charge resides in the nucleus.
• Electrons revolve around the nucleus in circular paths.
• The size of the nucleus is very less as compared to the size of atom.