Question about the Bohr model of atom and and electron in an orbital

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Discussion Overview

The discussion revolves around the behavior of electrons in the Bohr model of the atom when they gain energy, particularly through interactions with photons. Participants explore the implications of energy gain on the electron's potential and kinetic energy, as well as the nature of atomic orbitals.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant questions whether gaining energy causes an electron to move further from the nucleus and slow down, or to speed up while remaining close to the nucleus.
  • Another participant asserts that generally, greater energy corresponds to electrons being further from the nucleus, applicable to both quantum mechanical orbitals and classical orbits.
  • A participant raises the idea that for a given energy, there are infinite pairs of velocity and distance, prompting a discussion on how energy increase affects these parameters.
  • It is noted that unlike classical orbits, quantum orbitals do not have well-defined trajectories, and expected values of radius and kinetic energy must be calculated.
  • One participant mentions that excessive energy can ionize the atom, releasing the electron from any bound orbital.
  • Another participant suggests that higher energy levels lead to a greater expected radius, questioning why electrons do not simply move faster in their orbits.
  • A later reply introduces a classical analogy involving comets, discussing how collisions can change velocity and energy states, and relates this to atomic behavior in excited states.

Areas of Agreement / Disagreement

Participants express multiple competing views regarding the relationship between energy, velocity, and distance of electrons in the Bohr model. The discussion remains unresolved, with no consensus on the specific dynamics of energy gain.

Contextual Notes

Participants highlight the need to consider the implications of the Schrödinger equation on orbital behavior and the relationship between kinetic and potential energy, particularly in the context of classical analogies.

aaronll
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I have a question about what happen when an electron in the Bohr model of atom, gains energy because for example is "hitting" by a photon.
Electron have an energy, and it is the sum of potential and kinetic.
When they gain energy, they gain potential energy so they go further away from nucleus and become slower, or they gain kinetic energy so they become faster but near to nucleus? and why?
thanks
 
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aaronll said:
I have a question about what happen when an electron in the Bohr model of atom, gains energy because for example is "hitting" by a photon.
Electron have an energy, and it is the sum of potential and kinetic.
When they gain energy, they gain potential energy so they go further away from nucleus and become slower, or they gain kinetic energy so they become faster but near to nucleus? and why?
thanks
In general, the greater the energy the further the electron is from the nucleus. This is true for QM atomic orbitals - and also true for classical orbits in an inverse square potential.
 
PeroK said:
In general, the greater the energy the further the electron is from the nucleus. This is true for QM atomic orbitals - and also true for classical orbits in an inverse square potential.
Thank you
But my question is because for an energy E i think there is ( if the orbit is circular with a definite radius r) an "infinite" amount of pairs of velocity and distance (v,r) with the same energy, so in what way when energy increase the electron be?
higher speed? higher potential?
 
aaronll said:
Thank you
But my question is because for an energy E i think there is ( if the orbit is circular with a definite radius r) an "infinite" amount of pairs of velocity and distance (v,r) with the same energy, so in what way when energy increase the electron be?
higher speed? higher potential?
Unlike the classical case, the orbitals are not well-defined trajectories. So, you have to calculate the expected values of ##r## and kinetic energy. These, however, follow the same principle that higher energy levels correspond to a greater expected value of ##r##.

It should be clear that if you give an electron too much energy then the atom is ionised and the electron is released - i.e. the energy takes it beyond any bound orbital.
 
PeroK said:
Unlike the classical case, the orbitals are not well-defined trajectories. So, you have to calculate the expected values of ##r## and kinetic energy. These, however, follow the same principle that higher energy levels correspond to a greater expected value of ##r##.

It should be clear that if you give an electron too much energy then the atom is ionised and the electron is released - i.e. the energy takes it beyond any bound orbital.
Maybe is the fact that higher energy levels correspond to a greater expected value of r, why the electron doesn't become only "quicker" around the orbit?
 
aaronll said:
Maybe is the fact that higher energy levels correspond to a greater expected value of r, why the electron doesn't become only "quicker" around the orbit?
... because the orbitals must satisfy the Schroedinger equation.
 
PeroK said:
... because the orbitals must satisfy the Schroedinger equation.
Ok... that is.
Thank you
 
Maybe it is interesting to first consider the classical case, e.g. a comet being hit by another one. This will primarily induce a change of the comets velocity including it's direction. If the comet was on a circular orbit before the collision, it will end up on an elliptical or even unbound hyperbolical orbit after the collision. On an elliptical orbit, both kinetic and potential energy will periodically change (anticyclically) between their maximum and minimum values.
By the virial theorem, however, their average values are always related as 2<T> = -<V>, at least for the bound elliptical orbits.
So besides a change in energy, there will in general be a change in angular momentum, which is also true in the atomic case.
The classical theory applies also to atoms if they are in highly excited states, so called Rydberg atoms.
 

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