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Niels Bohr's model of the atom

On the basis of the atomic model by Ernest Rutherford (1871-1937), Niels Bohr (1885-1962) developed a shell model with which the contradiction between classical physics and quantum theory should be balanced out through postulates. The performance of the model was shown in the quantitative interpretation of the spectra of the hydrogen atom, but its limits in the interpretation of the spectra of atoms with several electrons - . The Bohr model of the atom was then refined by Arnold Sommerfeld (1868-1951) and can therefore also be used for multi-electron systems.

With this simple atomic model according to Bohr and Sommerfeld, electron configurations can be set up and many connections between the structure of the electron shell and the properties of the elements in the periodic table can be established. However, it contradicts the laws of classical physics and cannot be used to explain the atomic bond.

The question of the internal structure of matter has preoccupied people since - - ancient times when Greek natural philosophers created the term atom for the smallest, indivisible particles from which matter is built. This model of the atom was only further developed by John Dalton (1766-1844) in the 19th century. Dalton concluded from experimental investigations that atoms are small, elastic, mass-filled, uncharged spheres that can neither be formed nor destroyed in chemical reactions, but can only be combined with one another in new ways.

With increasingly powerful scientific methods, the internal structure of the atoms was further investigated. On the basis of his famous scattering experiment, E. Rutherford  formulated the planetary model named after him in 1911. For the first time, this contains the statement that the mass of the atom is mainly localized in the atomic nucleus and that the negative electrons circle around the positive nucleus. According to the laws of classical physics, atoms should not be stable because positive and negative particles attract each other and the electrons should therefore actually crash into the positively charged atomic nucleus. In addition, the line spectra of hydrogen found by JJ Balmer had shown that the atomic shell is much more finely structured than assumed by Rutherford  .

To clarify these contradictions, the Danish physicist Niels Bohr developed a new, more powerful atomic model  ( english home work help - try it). He used the first findings of modern quantum mechanics and formulated so-called postulates in which he assumed that the laws of classical physics in the atomic area do not apply and must be replaced by other laws.

The basic idea was initially a dynamic balance between the Coulomb force and the centrifugal force. If the electrons orbit the nucleus in stable orbits, the centrifugal force must be exactly the same as the attraction of the electron due to the positive nuclear charge. By equating the forces and taking into account the orbital angular momentum of the electrons, Bohr was able to calculate the radius of the electron orbits in the hydrogen atom.

Read more:

Atoms, structure

Interpretation of line diagrams

The introductory guide to learning programming

Niels Henrik Abel

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