RUTHERFORD MODEL OF ATOM – HISTORY, FACTS

About Rutherford Model of Atom

Rutherford model of Atom, By the 19th century, enough evidence had accumulated in favor of the atomic hypothesis of matter. In 1897, the experiments on electric discharge through the gases carried out by Thompson. It revealed that the atoms of different elements contain negatively charged electrons that are identical for all the other atoms. However, an atom on a whole is electrically neutral. Therefore, the atom must contain some positive charge to neutralize the negative charge of the electrons. The 1st model was prepared by j j Thomson. According to the model, the positive charge of the atom is uniformly distributed throughout the quantity of the atom and the charged electrons area unit embedded in it just like the seeds of watermelon.

HISTORY:

We know that the condensed matter and dense gases at all temperatures emit nonparticulate radiation in which a continuous distribution of many wavelengths are present even though they’re present in several intensities. The radiation is considered to be due to the oscillations of atoms and molecules that are governed by the interaction of each molecule or atoms with its neighbors. In contrast, light emitted from rarefied gases heated in a flame or excited electrically in a glow tube-like neon that has only discrete wavelengths. In such gases the radiations emitted may be considered due to the individual atoms rather than because of the interactions between the atoms and the molecules.

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SOME MORE FACTS:

In the 19th century, it was also established that each element is associated with a characteristic’s spectrum of radiation. The fact suggested an intimate relationship between the internal structure of the atom and the spectrum of radiation emitted by it. Since the hydrogen is the simplest of all the elements known as well as we shall consider its spectrum in detail.

ALPHA PARTICLE SCATTERING AND RUTHERFORD’S NUCLEAR MODEL OF ATOM:

In Rutherford’s nuclear model of atoms, the entire electric charge and most of the mass of the atom is concentrated within the nucleus with the electrons a ways away. The electrons would be moving in orbits about the nucleus just as planets do around the sun. the trajectory derived by a particle depends on the impact parameter of the collision. The impact parameter is the perpendicular distance of the initial rate vector of the alpha particle from the center of the nucleus. A given beam of alpha particles has a distribution of impact parameters so that the beam is scattered in various directions with different probabilities.

ELECTRON ORBIT:

RUTHERFORD MODEL


The ruder ford nuclear model of the atom which involves classical concepts pictures the atom as an electrically neutral sphere consisting of a very small, massive and positively charged nucleus at the center surrounded by the revolving electrons in their respective dynamically stable orbits. The electrostatic force of attraction between the revolving electrons and the nucleus provides the required centripetal force to keep them in their orbits.

SPECTRAL SERIES:

We might expect that the frequency of the light emitted by a particular element would explain exhibit some regular patterns. Hydrogen is the simplest atom and therefore, has the simplest spectrum. In the observed spectrum, however, at 1st sight, there does not seem to be any resemblance to the order of regularity between the spectral lines. The line with the longest wavelength is the red light and the light with the shortest wavelength is the green light.

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BOHR’S MODEL OF HYDROGEN ATOM:

The model of the atom proposed by Rutherford assumes that the atoms consisting of the central nucleus and revolving around the electron are stable much like the sun-planet theory. However, there are some fundamental differences between the 2 situations. While the planetary system follows the gravitational force the nucleus-electron system being the charged particles interact with the coulomb’s law. There are few postulates, and they are:

The 1st postulate was that an electron in an atom could revolve around stable orbits without the emission of the radiant energy

The 2nd postulate defines the stable orbits the electrons move around the nucleus only in the angular momentum with certain integral multiple.

3rd postulate is incorporated into atomic theory the early quantum concepts developed by plank and Einstein.

ENERGY LEVEL:

RUTHERFORD MODEL


The energy of an atom is the least when the electron is revolving in an orbit closest to the nucleus. In that case, the absolute value of the energy is smaller and hence the energy is progressively larger in the outer orbits.

CONCLUSION:

Thus, I would like to conclude by saying that the atom as a whole is electrically neutral and therefore contains an equal amount of positive and negative charges. In Thompson’s model, it appeared as a spherical cloud of positive charges with electrons embedded in it. While in the Rutherford model it was known as most of the positive charge is concentrated in the center of the nucleus. Atoms of each element are stable and emit characteristic spectrum.

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