What is the difference between Bohr and Rutherford model? The former does not explain the energy levels in an atom while the latter provides an explanation of energy levels in an atom.
The structure of an atomic is explained using the Rutherford model and Bohr model. These atomic models provide a deeper scientific explanation of the atom’s properties.
We wrote this article to provide a detailed explanation into the differences and similarities between bohr and Rutherford model. Take the time to read the entire post for better understanding.
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Difference Between Bohr Model and Rutherford Model With Table
|Basic Terms||Bohr Model||Rutherford Model|
|Description||It is an atomic model that explains the movement of electrons in the energy levels or orbit located around the nucleus.||It is atom theory that states that an atom contains a central core where the entire mass is concentrated. Lightweight particles usually move around the core.|
|Observation||The model was developed based on observation of the line of spectra of the hydrogen atom||It was developed based on the observation of a gold foil experiment|
|Energy Levels||Describe the presence of discrete energy levels.||Does not describe the presence of discrete energy levels|
|Size of Orbit||The model explains the relationship between orbital size and energy of the orbital where the smallest orbital has the lowest energy||It does not offer an explanation of the relationship between orbital size and energy.|
|Postulates was given in the year||Niels Bohr in 1922||Ernest Rutherford in 1913|
|Electron frequencies||Emission of radiations of electrons is of specific frequencies||Emission of radiations of electrons is of all frequencies|
|Types of Emission Spectrum||It is in the line of the spectrum||It is a continuous spectrum|
What Is a Bohr Model?
The Bohr model, proposed by Danish physicist Niels Bohr in 1913, is a simplified model of the structure of atoms. It was developed to address the limitations of the earlier Rutherford model, which depicted electrons orbiting the nucleus in a manner similar to planets orbiting the sun.
Key features of the Bohr model include:
Electron Orbits: Bohr proposed that electrons orbit the nucleus in specific, quantized orbits, rather than in a continuous range of distances from the nucleus. Each orbit corresponds to a specific energy level.
Quantized Energy Levels: Electrons can only exist in these discrete orbits, and each orbit has a specific energy associated with it. Electrons can move between orbits by absorbing or emitting energy in discrete packets called quanta.
Angular Momentum Quantization: Bohr introduced the idea that an electron in a particular orbit has quantized angular momentum, meaning it can only have certain values.
Energy Absorption and Emission: Electrons absorb energy to move to higher energy orbits and emit energy when moving to lower energy orbits. The energy emitted or absorbed is quantized and corresponds to the energy difference between the initial and final orbits.
Bohr model had limitations. It couldn’t fully explain the spectra of atoms with more than one electron, and it didn’t incorporate the wave nature of electrons. The development of quantum mechanics in the 1920s and 1930s provided a more comprehensive understanding of atomic structure, supplanting the Bohr model. The modern quantum mechanical model describes electrons as existing within probability distributions called orbitals rather than in fixed orbits.
The postulation of Bohr Atomic Model
- Electrons move around the orbit shells or energy levels.
- Orbits are stationary to provide a fixed circular path
- Each orbit has a certain amount of energy and size
- The energy of the orbit is correlated to its size
- The smallest orbit has the lowest energy
- Radiation is either emitted or absorbed by electrons moving around the orbit shells
Shortcomings of Bohr Atomic Model
- Does not follow the Heisenberg Uncertainty Principle.
- Provide the inaccurate value of the orbital angular momentum.
- Does not provide a clear description of the spectra of larger atoms
- Does not explain the Zeeman Effect.
What Is a Rutherford Atomic Model?
The Rutherford atomic model, proposed by New Zealand-born physicist Ernest Rutherford in 1911, was a significant development in the understanding of atomic structure. Before Rutherford’s model, the prevailing idea was the Thomson model, which depicted the atom as a uniformly distributed “pudding” of positive charge with electrons embedded in it like raisins.
Rutherford’s experiments, notably the gold foil experiment conducted in collaboration with Hans Geiger and Ernest Marsden, provided evidence that led to a new atomic model. In the gold foil experiment, alpha particles were directed at a thin sheet of gold foil. According to the prevailing Thomson model, the alpha particles should pass through the foil with only slight deflections due to the diffuse positive charge. However, the actual results were surprising:
- Most of the alpha particles passed through the foil without deflection, indicating that most of the atom is empty space.
- Some alpha particles were deflected at large angles, and a small fraction even bounced straight back. This suggested that the positive charge in the atom is concentrated in a small, dense nucleus.
Based on these findings, Rutherford proposed a new atomic model with the following features:
Nucleus: The atom has a small, dense, and positively charged nucleus at its center, where nearly all the mass of the atom is concentrated.
Electron Orbits: Electrons orbit the nucleus, much like planets orbiting the sun. However, Rutherford’s model didn’t specify how electrons were distributed in these orbits.
While the Rutherford model successfully explained the results of the gold foil experiment and introduced the concept of a nucleus, it had limitations. It couldn’t explain the stability of atoms and why electrons, which are negatively charged, don’t rapidly spiral into the positively charged nucleus due to electromagnetic attraction.
The Bohr model, proposed a few years later, addressed some of these shortcomings by introducing quantized electron orbits and specific energy levels. The Bohr model was a transitional step toward the more advanced quantum mechanical model of the atom.
Postulation for Rutherford Atomic Model Using Gold Foil Experiment
- Atoms are present in the nucleus and they are positively charged
- The nucleus of the atom is surrounded by negatively charged particles
- An atom is inert or electrically neutral
- An atom is bigger than the nucleus
Shortcomings of Rutherford Atomic Model
- Not suitable for explaining the electromagnetic theory
- Unclear explanation about the line of spectrum and stability of an atom
- Poor description of the electron’s arrangement
Main Difference between Bohr and Rutherford Model
- Bohr model was postulated in 1922 whereas the Rutherford model in 1913.
- Bohr model observation is based on the line of spectra of the hydrogen atom whereas Rutherford model observation are based on gold foil experiment
- Rutherford model does not explain the presence of discrete energy levels while the Bohr model explains the presence of discrete energy levels
- Bohr model provides a relationship between orbit energy and size whereas the Rutherford model does not offer a description between orbit energy and size
- Bohr model emission occurs in the line of the spectrum whereas the Rutherford model is a continuous spectrum
The Bohr and Rutherford models represent crucial stages in the historical development of our understanding of atomic structure. The Rutherford model, proposed in 1911, introduced the concept of a central nucleus containing most of the atom’s mass, based on experimental evidence from the gold foil experiment. This departure from the previous Thomson model laid the groundwork for a more accurate description of atomic architecture.
The Bohr model, proposed by Niels Bohr in 1913, further refined the understanding of electron behavior within the atom. Bohr introduced the idea of quantized electron orbits and specific energy levels, addressing some of the limitations of the Rutherford model. The Bohr model successfully explained the spectral lines of hydrogen, but it had its own set of limitations, such as its inability to account for the behavior of atoms with more than one electron.
Both models were crucial in shaping the evolution of atomic theory, with the Rutherford model highlighting the presence of a nucleus and the Bohr model introducing quantization in electron orbits. However, as scientific exploration progressed, the inadequacies of these models became apparent. The advent of quantum mechanics in the 1920s provided a more comprehensive and accurate framework for understanding the behavior of electrons within atoms.
The quantum mechanical model, which incorporates the wave-particle duality of electrons and the concept of probability distributions in orbitals, has become the foundation of modern atomic theory. The Bohr and Rutherford models, while valuable milestones, are now viewed as simplified representations that paved the way for a more sophisticated understanding of the intricacies of atomic structure.
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