Bohr’s Model

The Bohr model states that electrons revolve around the nucleus at constant energy levels. Progressive orbits from the nucleus exist at high energy levels. When electrons return to a low energy level, they emit energy in the form of light. Electrons revolve around the nucleus in an orbit of fixed size and strength. The strength of an orbit is related to its size. Low power is found in very small orbits. Radiation is absorbed or released when an electron moves from one orbit to another.

THEORY

Bohr theory works by modifying the atomic structure model by explaining that electrons travel in fixed orbitals (shells) and not anywhere in between and also explained that each orbit (shell) has a constant energy level. Rutherford essentially defined the atomic nucleus and Bohr transformed that model into electrons with their energy levels.

Bohr’s model of Atom

The Bohr model consists of a small nucleus (positively charged) surrounded by negative electrons that travel around the nucleus in orbits. Bohr found that electrons located far from the nucleus have more energy, and electrons near the nucleus have less energy.

In an atom, electrons  rotate a positively charged nucleus in a straight circle called orbits or shells.

Each orbit or shell has a constant force and these circular motions are known as orbital shells.

Power levels are represented by a whole number (n = 1, 2, 3…) known as quantum numbers. This quantum numerical range starts at the side of the nucleus with n = 1 with the lowest energy level. Routes n = 1, 2, 3, 4… are given as K, L, M, N…. shells and when the electron reaches a low energy level, it is said to be in a low state.

The electrons in the atom go from low energy to high energy by getting the required energy and the electron goes from high energy to low energy levels by losing energy.

Bohr’s Model Atom Limits

• Bohr’s atomic model failed to explain the Zeeman Effect (effect of a magnetic field on the atomic spectra).

• It also failed to explain the Stark effect (the effect of electric field on the atomic spectra).

• Violates Heisenberg’s Uncertainty Policy.

• Could not define spectra obtained from large atoms

BOHR’S ATOMIC MODEL

Niels Bohr proposed the Bohr Model of the Atom in 1915. Because the Bohr Model is a replacement for the former Rutherford Model, some people call the Bohr’s Model a Rutherford-Bohr Model. The modern atomic model is based on quantum mechanics. The Bohr Model contains some errors, but it is important because it explains many of the accepted aspects of atomic theory apart from all the advanced statistics of the modern version. Unlike previous models, the Bohr Model defines Rydberg’s formula for spectral emission spectral lines.

The Bohr Model is a planetary model in which electrons have negative charges orbiting a small nucleus, with a positive charge similar to the planets orbiting the sun (except that the orbits do not plan). The gravitational force of the solar system is similar to the Coulomb (electric) force between a nucleus with a positive charge and negatively charged electrons.

BOHR’S THEORY

Bohr Model Key Highlights

Electrons revolve around the nucleus in an orbit of fixed size and strength.

The strength of an orbit is related to its size. Low power is found in very small orbits.

Radiation is absorbed or released when an electron moves from one orbit to another.

Bohr’s Hydrogen Model

The simplest example of a Bohr Model is a hydrogen atom (Z = 1) or a hydrogen-ion ion (Z> 1), in which an electron with negative charges surrounds a small positive nucleus. The magnetic field will be absorbed or released if the electron moves from one orbit to another. Only certain electron orbits are allowed. The potential radius of radiation increases as n2, where n is the prime quantum number. Version 3 → 2 produces the first line of the Balmer series. With hydrogen (Z = 1) this produces a wavelength of 656 nm (red light).

Bohr’s Model With More Heavy Atoms

Heavy atoms contain more protons in the nucleus than hydrogen atoms. More electrons were needed to cancel the positive charge of all these protons. Bohr believed that each orbit of an electron could hold a fixed number of electrons. Once the level was full, more electrons would be carried to the next level. Thus, the Bohr model of heavy atoms defines the electron shells. The model described some of the atomic structures of heavy atoms, which had never been produced before. For example, the shell model explained why atoms become smaller in the period (line) of the periodic table, even though they contained more protons and electrons. He also explained why high-energy gasses are ineffective and why atoms on the left side of the table occasionally attract electrons, while those on the right are missing. However, the model assumed that the electrons in the shells did not interact and could not explain why the electrons appeared to accumulate in an unusual way.

Problems With Bohr’s  Model

It violates Heisenberg’s Uncertainty Policy because it considers electrons to have both known radiation and orbit.

The Bohr model provides an incorrect value for the angular pressure of the lower extremity.

Make bad predictions about the spectrum of large atoms.

It does not predict the relative stiffness of spectral lines.

The Bohr Model does not define the ideal structure and hyperfine structure in spectral lines.

It does not define the Zeeman Effect.

Refinement and Bohr Model Development

The most striking refinement of the Bohr model was the Sommerfeld model, sometimes called the Bohr-Sommerfeld model. In this model, electrons travel in elliptical lines around the nucleus rather than in circular lines. The Sommerfeld model was better at describing the effects of spectral atoms, similar to the Stark effect on dividing the spectral line. However, the model could not accept the quantum magnetic number.

Finally, the Bohr model and Bohr – Sommerfeld model were replaced by the Wolfgang Pauli model based quantum machine in 1925. That model was developed to produce a modern model, introduced by Erwin Schrodinger in 1926. Today, the behavior of a hydrogen atom is defined using wave mechanics to describe atomic orbitals.

CONCLUSION

Bohr theory is applied to types such as H that contain only one electron e.g. Li2+. Bohr theory works on hydrogen as atoms (single electron system). Li2+ and H-atoms contain only one electron. For him, He2+ contains 2, 0 electrons, respectively. Bohr’s work has had a profound effect on our modern understanding of the internal functioning of the atom. However, his model worked well as a description of the hydrogen atom emission, but it was very limited when used in other atoms. Shortly after Bohr published his model of the atomic planet, several new discoveries were made, resulting in another revised atomic theory.