According to Dalton, atom is the smallest particle of matter. But atom contains smaller particles inside. Arrangement of these subatomic particle inside an atom, was proposed by many scientists. These are the different atomic models. Write an account of these models under the headlines given below.
1. Thomson's atomic model
2. Rutherford model of atom
3. Bohr model of atom (with diagrams of first 20 elements).
Answers
THOMSON'S ATOMIC MODEL:-
In 1898, J. J. Thomson proposed the first of many atomic models to come. He proposed that an atom is shaped like a sphere with a radius of approximately 10-10m, where the positive charge is uniformly distributed. The electrons are embedded in this sphere so as to give the most stable electrostatic arrangement.
An important aspect of this model is that it assumes that the mass of the atom is uniformly distributed over the atom. Thomson’s atomic model was successful in explaining the overall neutrality of the atom. However, its propositions were not consistent with the results of later experiments. In 1906, J. J. Thomson was awarded the Nobel Prize in physics for his theories and experiments on electricity conduction by gases
RUTHFORD MODEL OF ATOM:-
According to the Rutherford atomic model: The positively charged particles and most of the mass of an atom was concentrated in an extremely small volume. He called this region of the atom as a nucleus. ... He also claimed that the electrons surrounding the nucleus revolve around it with very high speed in circular paths.The Rutherford model was devised by Ernest Rutherford to describe an atom. Rutherford directed the Geiger–Marsden experiment in 1909 which suggested, upon Rutherford's 1911 analysis, that J. J. Thomson's plum pudding model of the atom was incorrect.
BOHR MODEL OF ATOM
The modern model of the atom is based on quantum mechanics. ... The Bohr Model is a planetary model in which the negatively charged electrons orbit a small, positively charged nucleus similar to the planets orbiting the sun (except that the orbits are not planarOverview of the Bohr Model
Niels Bohr proposed the Bohr Model of the Atom in 1915. Because the Bohr Model is a modification of the earlier Rutherford Model, some people call Bohr's Model the Rutherford-Bohr Model. The modern model of the atom is based on quantum mechanics. The Bohr Model contains some errors, but it is important because it describes most of the accepted features of atomic theory without all of the high-level math of the modern version. Unlike earlier models, the Bohr Model explains the Rydberg formula for the spectral emission lines of atomic hydrogen.
The Bohr Model is a planetary model in which the negatively charged electrons orbit a small, positively charged nucleus similar to the planets orbiting the sun (except that the orbits are not planar). The gravitational force of the solar system is mathematically akin to the Coulomb (electrical) force between the positively charged nucleus and the negatively charged electrons.
Main Points of the Bohr Model
- Electrons orbit the nucleus in orbits that have a set size and energy.
- The energy of the orbit is related to its size. The lowest energy is found in the smallest orbit.
- Radiation is absorbed or emitted when an electron moves from one orbit to another.
