How did Rutherford, bohr, and quantum geiger-marden metail-foil experiments contradict thomas's raisin pudding model of the atom?
To understand how Rutherford, Bohr, and the Quantum-Geiger-Marsden metal-foil experiments contradicted Thomson's raisin pudding model of the atom, it is crucial to examine each of their contributions individually.
1. Rutherford's Experiment:
Rutherford conducted the famous gold foil experiment in 1911. In this experiment, he bombarded a thin sheet of gold foil with alpha particles (positively charged particles). According to Thomson's raisin pudding model, the positive charge and mass of the atom were spread uniformly, much like the raisins in a pudding. Consequently, most of the alpha particles should have passed through the gold foil with only a slight deflection due to the positive "pudding" in the atom.
However, Rutherford's observations contradicted this model. He found that while most of the particles did go straight through, some were significantly deflected and even bounced back at various angles. This unexpected result led Rutherford to propose a new model for the atom.
2. Bohr's Model:
After Rutherford's discovery, Niels Bohr built upon it by proposing his model of the atom in 1913. Bohr suggested that electrons orbited the nucleus in distinct energy levels or shells. He also introduced the concept of quantized energy, stating that electrons could only occupy specific energy levels and transition between them by absorbing or emitting specific amounts of energy.
Bohr's model accounted for the experimental evidence and helped explain why the negatively charged electrons did not crash into the positively charged nucleus, as classical physics would predict. This model laid the foundation for our understanding of atomic structure and the behavior of electrons.
3. Quantum Geiger-Marsden Experiment:
The Quantum-Geiger-Marsden experiment was a refinement of Rutherford's gold foil experiment conducted by Geiger and Marsden in 1909. They observed the scattering of alpha particles from a thin sheet of gold foil and measured their angles of deflection.
Similar to Rutherford's findings, the experiment showed that a small fraction of the alpha particles experienced significant deflection, which directly contradicted Thomson's model. This outcome provided additional support for Rutherford's idea of a dense, positively charged nucleus at the center of the atom.
In summary, Rutherford's gold foil experiment demonstrated that the positive charge of the atom was concentrated in a small, dense nucleus, unlike Thomson's homogeneous model. Bohr's model further developed this idea by proposing specific energy levels for the electrons, explaining the stability of the atom. The Quantum Geiger-Marsden experiment reinforced Rutherford's findings by confirming the deflection of alpha particles and ruling out the raisin pudding model.