What is the relationship between energy and position in quantum mechanics?

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In summary: I'm not sure if that last part really belongs here or not, so don't take too much from it.)In summary, the energy of the electron in a hydrogen atom can have an exact value even though its position is variable due to the uncertainty principle. This is because the variation in momentum compensates for the variation in position, allowing for the exact energy value to be maintained. This concept is better understood when considering wavefunctions and operators.
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Sacroiliac
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In the hydrogen atom the 1s orbital has a clearly defined energy of 13.6 eV, but the probability density and radial probability density says you are liable to find the 1s electron anywhere from the nucleus on out.

How does this exact energy value jive with this variable position?
 
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does the law really say that the electron can be found in this range?
 
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The energy of the atom

can be exact with the position not being exact because the canonical conjugate to the the position, the momentum, also varies. To put it very crudely, the variation in the momentum compensates for the variation in position, allowing the energy to have an exact value.

That's about as good an answer as I can come up with under the circumstances, but when you learn a little more about wavefunctions and operators and such you'll understand it better.
 
  • #4
Originally posted by Sacroiliac
In the hydrogen atom the 1s orbital has a clearly defined energy of 13.6 eV, but the probability density and radial probability density says you are liable to find the 1s electron anywhere from the nucleus on out.

How does this exact energy value jive with this variable position?

Yes. That's quite correct. The probability density decreases as you go further from the nucleus of the atom but it never becomes zero. The electron can tunnel into the potential barrier, i.e. into the classically forbidden regions. The farther it travels into such a region the shorter the time it stays there. The time-energy uncertainty principle implies that the ectron will not stay outside the barrier for a time equal to or greater than the time it takes to measure an energy violation.

Pete
 
  • #5


Originally posted by Tyger
can be exact with the position not being exact because the canonical conjugate to the the position, the momentum, also varies. To put it very crudely, the variation in the momentum compensates for the variation in position, allowing the energy to have an exact value.


Are you saying that as the particle gets closer to the nucleus its potential energy decreases but because it is more localized the HUP causes its momentum to increase and exactly offset the decrease in Potential energy?

PMB I didn't understand your post. Sorry.
 
  • #6


Originally posted by Sacroiliac
Are you saying that as the particle gets closer to the nucleus its potential energy decreases but because it is more localized the HUP causes its momentum to increase and exactly offset the decrease in Potential energy?

I did say that was a very crude description, but the basic idea is correct. You see, we can't really say the electron has a specific momentum or position because its wavefunction is spread out in space around the proton. But while it is spread out in both coordinate space and momentum space the phase of its amplitude changes with time at a constant rate, so its energy is well defined.
 

What is the concept of energy in quantum mechanics?

In quantum mechanics, energy is a fundamental quantity that describes the state of a system. It can exist in discrete amounts, known as energy levels, and can be transferred between particles or converted into different forms. Energy in quantum mechanics is described by the Hamiltonian operator, which is used to calculate the total energy of a system.

What is the Heisenberg uncertainty principle and how does it relate to energy and position in quantum mechanics?

The Heisenberg uncertainty principle states that it is impossible to simultaneously know the exact position and momentum of a particle. This also applies to energy and position in quantum mechanics, as the more precisely we measure the position of a particle, the less we know about its energy and vice versa. This principle is a fundamental aspect of quantum mechanics and is related to the probabilistic nature of particles at the quantum level.

How does the concept of energy levels in quantum mechanics differ from classical mechanics?

In classical mechanics, energy is considered to be continuous and can take on any value. However, in quantum mechanics, energy is quantized, meaning it can only exist in discrete amounts or levels. This is due to the wave-particle duality of particles at the quantum level and is a key difference between classical and quantum mechanics.

How does the position of a particle affect its energy in quantum mechanics?

In quantum mechanics, the position of a particle is described by a wave function, which represents the probability of finding the particle at a certain position. The position of a particle can affect its energy, as the wave function and energy are related through the Schrödinger equation. Changes in the position of a particle can lead to changes in its energy level, which can be observed through phenomena such as quantization and tunneling.

What is the relationship between energy and potential energy in quantum mechanics?

In quantum mechanics, potential energy is a form of energy that is associated with the position of a particle within a potential field. This potential energy can affect the total energy of a system and is related to the Hamiltonian operator. By solving the Schrödinger equation, we can determine the energy levels and potential energy of a particle in a given system, providing insight into its behavior and properties.

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