Structure of Atoms and Nuclei — Physics STD 12 Science — Question
Maharashtra BoardEnglish MediumSTD 12 SciencePhysicsStructure of Atoms and Nuclei4 Marks
Question
State the difficulties faced by Rutherford’s atomic model.
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Answer
(1) According to Rutherford, the electrons revolve in circular orbits around the atomic nucleus. The circular motion is an accelerated motion. According to the classical electromagnetic theory, an accelerated charge continuously radiates energy. Therefore, an electron during its orbital motion, should go on radiating energy. Due to the loss of energy, the radius of its orbit should go on decreasing. Therefore, the electron should move along a spiral path and finally fall into the nucleus in a very short time, of the order of $10^{-16} s$ in the case of a hydrogen atom. Thus, the atom should be unstable. We exist because atoms are stable.
(2) If the electron moves along such a spiral path, the radius of its orbit would continuously decrease. As a result, the speed and frequency of revolution of the electron would go on increasing. The electron, therefore, would emit radiation of continuously changing frequency, and hence give rise to a con-tinuous spectrum. However, atomic spectrum is a line spectrum.
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