Bohr’s Model for Hydrogen Atom

In 1913, Niels Bohr proposed a quantized shell model of an atom in order to provide an explanation for how electrons can maintain a stable orbit around the nucleus. Due to the emission of electromagnetic radiation by the charged particles, this model was able to alleviate the instability problem associated with the previous Rutherford model of the atom, which displayed a motion in which electrons would lose their energy and subsequently spiral into the nucleus as a result of the loss of energy. According to Bohr, his model was supported by the classical laws of physics as well as the quantum theory of radiation.

Similarly, to the motion of planets around the sun, Niels Bohr’s atomic theory has electrons with fixed sizes and energies travelling in orbits around a positively charged nucleus, analogous to the motion of planets around the sun. It is possible to summarise Bohr’s atomic model by stating that the energy levels of the electrons are mostly determined by the size of their orbital planes. As a result, electrons with lower energy will be found in smaller orbits. The reason why atoms are unstable is because electrons hop to lower orbits, generating radiation in the process. Now, an atom on the smallest orbit will be fully stable since the electron will not be able to jump to a lower orbit because there will be no lower orbit for it to jump to. As a result, it was postulated that an electron may move between these orbits by gaining or releasing photons, depending on the situation (energy).

Postulates of the Bohr Atomic Model

The following are the most important characteristics of Niels Bohr’s atomic model, as described by him.

• In an atom, negatively charged electrons orbit around a positively charged nucleus, forming a ring. These electrons travel in precise circular trajectories, which are referred to as orbits or shells.
• In this atomic model, each of the circular routes has a fixed level of energy, which is referred to as an orbital shell in the atomic model.
• Quantum numbers are used to describe the energy levels of electrons in different orbits. They are represented by the integers n=1, 2, 3… and are referred to as quantum numbers. This is done by assigning numbers to the shells such as K for 1, 2, 3, 4, and L for 2, 3 and 4 accordingly. The lowest energy level of an electron is n=1, which is the level that is closest to the nucleus and is sometimes referred to as the ground state of the electron.
• Increasing the amount of energy (or photons) available to an electron allows it to move to a higher-energy orbital shell, while decreasing the amount of energy available allows it to jump to a lower-energy level or orbital shell.

Hydrogen Energy Levels

The Bohr model is used to describe the structure of hydrogen energy levels, and it is based on quantum mechanics. The shell structure depicted in the figure below is associated with each of the principal quantum numbers represented by the shells. The energy levels displayed match to the shells on the screen. The quantity of energy in each level is expressed in electron volts (eV), with the maximum energy equal to the ionisation energy of 13.598eV at the highest level.

The Hydrogen Spectrum

The functional and structural creation of a hydrogen atom, as well as its energy levels, are explained using the Neil Bohr atomic model developed by Niels Bohr. Each orbital shell corresponds to a quantum number ‘n’ that corresponds to a set of energy levels in the corresponding orbital shell. The unit amount of each energy level is represented by the symbol eV. The ionisation energy of 13.598 eV is the highest possible energy level that an orbital shell can have.

Because of this, whenever electrons move between the different energy levels in a hydrogen atom, they generate what’s known as a spectrum. This means that the transmission of light occurs as a result of the transfer of electrons between different energy levels. In a hydrogen atom, there are four different wavelengths of visible light that are present in the visible spectrum of light. It is this state of electrons that is defined by the Balmer equation, which refers to the excited state of electrons that transitions down to a minimum of n=2.

Limitations of Bohr’s Model of the Hydrogen Atom.

Moreover, it is in violation of the Heisenberg Uncertainty Principle. According to the Neils Bohr atomic model theory, electrons have both known position and known momentum at the same time, which is inconceivable according to Heisenberg’s principle of uncertainty.

• The Bohr atomic model did not produce accurate predictions for large-sized atoms and only supplied sufficient information for smaller-sized atoms, according to the findings.
• When the spectrum is divided into a few wavelengths within the sight of a magnetic field, it does not clarify the Zeeman impact.

If the spectrum is divided into almost insignificant lines within the range of an electric field, the Stark effect is not clarified.

Conclusion

Bohr’s atomic model was considered to be the forerunner of quantum mechanical models. It is only applicable to H-like species (single electron system), such as Li2+, that this theory of the atomic model can be applied. The postulates and limitations of this atomic model are discussed in detail in this article. Understanding alternative atomic models suggested by other scientists becomes easier as a result of this model.