Bohr's Atomic Model

Manocha Academy・2 minutes read

Niels Bohr's atomic model revolutionized atomic theory by addressing the stability of atoms and the observation of line spectra. Bohr proposed fixed circular orbits for electrons with quantized angular momentum, rectifying previous models' issues like Rutherford's inability to explain atom stability.

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Neils Bohr's atomic model revolutionized atomic theory by introducing fixed circular orbits for electrons, quantized angular momentum, and energy transitions between shells, addressing the stability of atoms and line spectra observations.
The formula to calculate the radius of electron shells, V, kinetic energy, potential energy, and total energy provides a comprehensive understanding of electron behavior in Bohr's atomic model.
The concept of quantized energy levels in Bohr's model explains the line spectrum phenomenon, where only specific energy values are accepted, leading to the emission of light of distinct colors and frequencies during electron transitions.

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Recent questions

What is Bohr's atomic model?
Electrons revolve in fixed orbits around the nucleus.
What is the significance of Bohr's model?
It explains atomic stability and line spectra observations.
How do electrons transition in Bohr's model?
Electrons move between fixed energy orbits by absorbing or emitting radiation.
What is the formula for calculating electron energy levels?
Total energy equals -3.6 * Z² / n² electron volts.
How does Bohr's model explain the atomic spectrum?
Electrons emit specific colors and wavelengths due to quantized energy levels.

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Summary

00:00

Bohr's Atomic Model Revolutionizes Atomic Theory

Neils Bohr, a famous scientist who challenged Albert Einstein, has an element named after him and won the Nobel Prize for his work on the structure of the atom.
Bohr's atomic model focuses on electrons revolving in fixed orbits around the nucleus in shells or orbits labeled as K, L, M, and so on.
Various atomic models have been proposed over the years, starting with Dalton's solid sphere model in 1807, followed by Thomson's plum pudding model in 1897, and Rutherford's nuclear model after the discovery of the nucleus.
Rutherford's model faced drawbacks as it couldn't explain the stability of the atom or the observation of line spectra in elements like hydrogen.
Bohr's model rectified these issues by introducing the concept of electrons moving in fixed circular orbits with quantized angular momentum.
The first postulate of Bohr's model states that electrons revolve in fixed circular orbits with fixed radius and energy, akin to planets orbiting the sun in the solar system.
The second postulate introduces a quantization condition where electrons can only revolve in orbits where the angular momentum is an integer multiple of H by 2π.
Electrons in Bohr's model can gain or lose energy, moving between shells, with the frequency of radiation absorbed or emitted during these transitions determined by the change in energy divided by Planck's constant.
Bohr's model revolutionized atomic theory by addressing the stability of atoms and the observation of line spectra, providing a more accurate representation of atomic structure.
Understanding Bohr's atomic model involves grasping the fixed orbits of electrons, the quantization of angular momentum, and the energy transitions between shells, crucial for comprehending the structure of atoms.

17:45

Atomic Model: Electron Orbits and Forces

The n integer represents the shell number in B's model of the atom.
Electrons revolve around the nucleus similar to planets around the Sun in the solar system.
The force responsible for electron movement is electrostatic, not gravitational.
Electrostatic force is the attraction between the positively charged nucleus and negatively charged electron.
The formula for electrostatic force is 1x4 Pi Epsilon q1 Q2 by r².
Centripetal force, acting as the center-seeking force, keeps the electron in orbit around the nucleus.
The electrostatic force is equivalent to the centripetal force in this scenario.
The centripetal force formula is MV ² by R for a particle in circular motion.
The expression for calculating the radius of the electron is RN = 0.53 n² by Z.
The radius of hydrogen shells can be determined using the formula RN = 0.53 n² by Z, with values for n and Z corresponding to the shell and atomic number, respectively.

35:26

Electron Shell Formulas for Energy Calculation

The formula to calculate the radius of the electron shell is R = 0.53 * n² / Z, where Z is the atomic number.
This formula is applicable for single electron species like H+ or Li+ by substituting the respective atomic numbers.
The velocity of the electron can be calculated using the formula V = 2.18 * 10^6 * Z / n m/s in the nth shell.
The kinetic energy of the electron is given by the formula KE = 13.6 * Z² / n² electron volts.
The potential energy of the electron in the nth shell is calculated as PE = -2 * KE, where KE is the kinetic energy.
The potential energy formula is PE = -2 * 13.6 * Z² / n² electron volts.
The negative sign in potential energy arises due to the electron's negative charge and the reference point of zero energy at infinity.
The total energy of an electron is the sum of its potential and kinetic energies, representing the energy due to motion and electrostatic forces.

52:35

"Electron Energy Levels in Atoms Explained"

The formula for potential energy is -2 * 13.6 * Z² / n², with a negative factor of two, while kinetic energy is 30 * 13.6 * Z² / n², both in electron volts.
Simplifying the formula results in a total energy of -3.6 * Z² / n² electron volts for the N shell of an atom, with negative total energy due to the electron losing energy as it approaches the nucleus.
Applying the total energy formula to the hydrogen atom's electron in different shells reveals the energy levels: -3.6 eV for the first shell, -3.4 eV for the second, -1.51 eV for the third, and -0.85 eV for the fourth shell.
Moving from lower to higher shells increases the electron's energy, as seen in the increasing negative values of energy levels.
The maximum energy of an electron occurs when it is very far from the nucleus, with a total energy of zero, making the electron free from the atom and turning the atom into a cation.
Bore's first postulate states that electrons in fixed circular orbits have fixed energy, while the third postulate explains how electrons can gain or lose energy when changing orbits.
Excitation occurs when an electron gains energy, moving to higher shells, while de-excitation happens when it loses energy, moving to lower shells.
Electrons require a specific amount of energy to move between energy levels, with a quantization principle dictating that only certain energy values are accepted.
Bore's model couldn't explain the atomic spectrum, characterized by a line spectrum of specific colors and wavelengths emitted when electrons gain or lose energy and release electromagnetic radiation.
The line spectrum phenomenon is due to electrons only accepting specific energy values, leading to the emission of light of certain colors and frequencies, as explained by Bore's model.

01:08:58

"Calculating Radiation Frequency and Atomic Models"

The frequency of radiation absorbed or emitted during electron transitions can be calculated using the formula: frequency (f) equals change in energy (Delta e) divided by Plank's constant (H), where H is 6.626 * 10^-34 J second. This formula helps determine the frequency of electromagnetic waves emitted or absorbed by dividing the energy difference by Plank's constant. Additionally, the wavelength of radiation can be calculated using the formula: velocity of the wave (c) equals frequency (F) times wavelength (Lambda), explaining the atomic spectrum and the fixed frequency energy bands observed.
Various atomic models have been proposed over the years, starting with John Dalton's atom model in 1807, followed by JJ Thompson's plum pudding model in 1897, and Ernest Rutherford's nuclear model in 1911. Niels Bohr's planetary model in 1913 addressed the limitations of Rutherford's model, but it also had drawbacks. Subsequently, the Schrödinger quantum model in 1926 was introduced, which will be discussed in a future video.

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