Postulates of Atomic Model of Bohr

bohr model

The atomic model of Bohr describes the structure of atoms, especially that of hydrogen, proposed in (1913) by the Danish physicist Niels Bohr. The Bohr atom model, which is a radical deviation from the previous classical descriptions, was the first to incorporate quantum theory and was the predecessor of purely quantum mechanical models.


What is the atomic model of Bohr?

In 1913, Bohr developed an atomic model abandoning the considerations of classical physics and taking into account the quantum theory of Max Planck.

Niels Bohr did not completely discard Rutherford’s planetary model but instead included additional restrictions. To begin with, he considered the concept of classical physics that an accelerated charge continuously emits radiation not applicable.

According to Planck’s quantum theory, the absorption and emission of energy take place in the form of photons or quanta. Bohr used this same idea to apply it to the atom; that is, the process of emission or absorption of radiation by an atom can only be carried out discontinuously, by means of photons or quanta that are generated by electronic jumps from one quantized state of energy to another.

4 Postulates of atomic model of Bohr

Bohr’s model is based on the following postulates, which are valid for atoms with a single electron such as hydrogen, and allowed to explain their emission and absorption spectra.

  1. First postulate: electron stability.
  2. Second Postulate: orbits or levels allowed
  3. Third Postulate: Energy levels of states.
  4. Fourth Postulate: emission and absorption of

Limitations of Bohr’s atomic model

  • The electrons spin in stable orbits around the nucleus. There is no radiant energy emission. Each orbit has defined energy called the energy layer or energy level.
  • An energy level or orbit has been designated as the shell K, L, M, N. It is said that an electron is in its fundamental state when it is in the lowest energy level.
  • When jumping from one orbit or energy level to another, the electron emits or absorbs energy. When the electron jumps from the energy envelope with greater energy to a lower energy layer of energy, the electron emits energy. But when the electron jumps from the lowest energy level to the highest energy level, the electron absorbs energy.
    The energy that is absorbed or emitted by the electron is equal to the difference between the energies of the two energy levels (E1, E2), which is then determined by the Plank equation.

Atomic model of Bohr hydrogen

Niels Bohr introduced the atomic hydrogen model in 1913. He described it as a nucleus with a positive charge, composed of protons and neutrons, surrounded by a cloud of electrons with a negative charge. In the model, electrons orbit around the nucleus in the atomic layers. The atom is held together by electrostatic forces between the positive nucleus and the negative environment.

Hydrogen energy levels

Bohr’s model is used to describe the structure of hydrogen energy levels. The image below represents the shell structure, where each shell is associated with the main quantum number n. The energy levels presented correspond to each shell. The amount of energy in each level is reported in eV, and the maximum energy is the ionization energy of 13,598eV.Images of the atomic model of Bohr

These are some of the images where you can see the atomic model of Bohr

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