Chapter 9: Problem 19
Use the virial theorem to obtain an expression for the relation between the mean kinetic and potential energies of an electron in a hydrogen atom.
Short Answer
Expert verified
For an electron in a hydrogen atom, the mean potential energy (\( \overline{V} \)) is twice the magnitude of the mean kinetic energy (\( \overline{T} \)) but with opposite sign, expressed by \( \overline{V} = -2\overline{T} \).
Step by step solution
01
Understanding the Virial Theorem
The virial theorem pertains to stable systems and relates the average total kinetic energy (\( \overline{T} \)) of a system to its average total potential energy (\( \overline{V} \)). For a bound system under the influence of inverse square forces, such as the electrostatic force between an electron and a nucleus, the virial theorem states that \( \overline{T} = -\frac{1}{2}\overline{V} \).
02
Apply the Virial Theorem to a Hydrogen Atom
In a hydrogen atom, an electron is subject to the Coulombic inverse-square force due to the nucleus (proton). Therefore, the virial theorem can be directly applied, and the mean kinetic energy (\( \overline{T} \)) of the electron is related to its mean potential energy (\( \overline{V} \)) by this relationship: \( \overline{T} = -\frac{1}{2}\overline{V} \).
03
Express the Relation
Solving for the mean potential energy in terms of the mean kinetic energy, the relation can be expressed as \( \overline{V} = -2\overline{T} \). Thus, the magnitude of the average potential energy of the electron is twice that of the average kinetic energy, but with opposite sign.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Mean Kinetic Energy
Mean kinetic energy is a fundamental concept in the study of quantum mechanics and plays a crucial role in describing the motion of particles. In the context of a hydrogen atom, which consists of a single electron orbiting a nucleus, the mean kinetic energy represents the average motion energy of the electron over time.
According to the principles of quantum mechanics, the position and momentum of an electron are not fixed but can be described by probability distributions. The mean kinetic energy, usually denoted as \( \overline{T} \), is a statistical average rather than a precise measurement at a single point in time.
This average provides insight into the typical behavior of the electron as it moves within the atom's electric field. Using the virial theorem, we can quantitatively relate the mean kinetic energy to the potential energy in such systems, providing a powerful tool for understanding atomic structure and the behavior of electrons.
According to the principles of quantum mechanics, the position and momentum of an electron are not fixed but can be described by probability distributions. The mean kinetic energy, usually denoted as \( \overline{T} \), is a statistical average rather than a precise measurement at a single point in time.
This average provides insight into the typical behavior of the electron as it moves within the atom's electric field. Using the virial theorem, we can quantitatively relate the mean kinetic energy to the potential energy in such systems, providing a powerful tool for understanding atomic structure and the behavior of electrons.
Mean Potential Energy
Mean potential energy, often symbolized as \( \overline{V} \), is a measure of the average energy an electron in a hydrogen atom has due to its position in the electric field generated by the nucleus. This is analogous to the energy a ball gains when lifted against the force of gravity, with the important distinction that in quantum systems like atoms, we are dealing with electric rather than gravitational fields.
The potential energy is negative because the electron is bound to the nucleus; as the electron gets closer to the nucleus, the system's energy decreases. The average of this energy over time, considering the probabilistic nature of the electron's position, is quantified as the mean potential energy. It reveals how the electron interacts with the atom's nucleus and allows for the prediction of energetic stability within the atom.
The potential energy is negative because the electron is bound to the nucleus; as the electron gets closer to the nucleus, the system's energy decreases. The average of this energy over time, considering the probabilistic nature of the electron's position, is quantified as the mean potential energy. It reveals how the electron interacts with the atom's nucleus and allows for the prediction of energetic stability within the atom.
Coulombic Inverse-Square Force
The Coulombic inverse-square force is central to our understanding of atomic structure and the behavior of charged particles like electrons and protons. This force describes the attraction or repulsion between two charged particles, decreasing in strength with the square of the distance between them.
In a hydrogen atom, the electron experiences an attractive force towards the positively charged nucleus, governed by Coulomb's law. This force has important implications: it dictates not only the electron's orbit but also how its energy levels are distributed.
Since this force is an inverse-square force, it fits perfectly with the virial theorem's applicability, allowing scientists to derive meaningful relationships between kinetic and potential energies within the atom.
In a hydrogen atom, the electron experiences an attractive force towards the positively charged nucleus, governed by Coulomb's law. This force has important implications: it dictates not only the electron's orbit but also how its energy levels are distributed.
Since this force is an inverse-square force, it fits perfectly with the virial theorem's applicability, allowing scientists to derive meaningful relationships between kinetic and potential energies within the atom.
Average Total Kinetic Energy
Average total kinetic energy in quantum systems like the hydrogen atom can be conceptually challenging since it pertains to the entire statistical ensemble of states the electron can occupy. It averages out all the kinetic energy values that an electron can have over time or different quantum states.
In the context of the virial theorem, the average total kinetic energy is of particular importance. For a hydrogen atom, when the virial theorem is applied, it allows us to derive a direct relationship with the average total potential energy, facilitating deeper insights into the energy dynamics and the stability of the atom.
In the context of the virial theorem, the average total kinetic energy is of particular importance. For a hydrogen atom, when the virial theorem is applied, it allows us to derive a direct relationship with the average total potential energy, facilitating deeper insights into the energy dynamics and the stability of the atom.
Average Total Potential Energy
The average total potential energy of an electron in a hydrogen atom reflects the cumulative effect of the electric field from the nucleus on the electron over all possible states. It is a measure of the energy needed to maintain the electron within the atom's potential well, and, like kinetic energy, is averaged considering the probabilistic nature of the electron's locations.
By using the virial theorem, we can see that the average total potential energy is directly related to the average total kinetic energy. This relationship is both predictive and explanatory, offering a window into how quantum systems manage energy and providing a foundation for understanding phenomena such as spectral lines and chemical bonding.
By using the virial theorem, we can see that the average total potential energy is directly related to the average total kinetic energy. This relationship is both predictive and explanatory, offering a window into how quantum systems manage energy and providing a foundation for understanding phenomena such as spectral lines and chemical bonding.