Rutherford’s model of an atom:
- Rutherford carried out an experiment where fast-moving alpha particles were made to fall on a thin gold foil. The following were his observations:
- Most of the fast moving α-particles passed straight through the gold foil.
- Some of the α-particles were deflected by the foil by small angles.
- Surprisingly one out of every 12000 particles appeared to rebound.
Following were his conclusions from the α-particle scattering experiment:
- Most of the space inside the atom is empty because most of the α-particles passed through the gold foil without getting deflected.
- Very few particles were deflected from their path, indicating that the positive charge of the atom occupies very little space.
- A very small fraction of α-particles were deflected by 1800, indicating that all the positive charge and mass of the gold atom were concentrated in a very small volume within the atom.
On the basis of his experiment, Rutherford put forward the nuclear model of an atom, which had the following features:
- There is a positively charged centre in an atom called the nucleus. Nearly all the mass of an atom resides in the nucleus.
- The electrons revolve around the nucleus in circular paths.
- The size of the nucleus is very small as compared to the size of the atom.
Drawbacks of Rutherford’s model of the atom:
- Was unable to explain the stability of an atom.
- The theory was incomplete as it did not mention anything about the arrangement of electrons in the orbit.
- Failed to explain line spectra of an atom.
Shaalaa.com | Structure of Atom (Rutherford Model)
In Rutherford’s experiment, generally the thin foil of heavy atoms, like gold, platinum etc. have been used to be bombarded by the α-particles. If the thin foil of light atoms like aluminium etc. is used, what difference would be observed from the above results?