What is the force responsible for bonding between atoms in a covalent molecule?

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Discussion Overview

The discussion centers on the forces responsible for bonding in covalent molecules, exploring the nature of electromagnetic interactions, electron behavior, and quantum mechanical effects. Participants examine various aspects of covalent bonding, including the role of electron density and the implications of the electromagnetic force.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants propose that the force keeping a covalent molecule together is related to electrons of opposite spins and lower energy states due to filled valence shells.
  • Others argue that the electromagnetic interaction is the primary force, where pulling one nucleus affects the electron orbital, allowing the second nucleus to follow.
  • A counterexample, H2+, is mentioned to illustrate that the bond forms because electrons interact with both nuclei, lowering their energy and reducing Coulomb repulsion.
  • Some participants express skepticism about the common description of electron density reducing Coulomb repulsion, suggesting that the attractive force between protons and electrons is more relevant.
  • There is a discussion about whether to consider the magnetic component of the electromagnetic force, with some asserting that it is mainly the electric part that is significant in this context.
  • Participants note that covalent bonding is a quantum mechanical effect, where electrons have more space to move, which reduces their momentum and kinetic energy due to the uncertainty principle.
  • There is a proposal that overlapping electron orbitals create a larger area of electron density, which attracts both nuclei and holds the molecule together.
  • Some participants clarify that the bond is not between electrons but rather due to the attraction between electrons and nuclei.

Areas of Agreement / Disagreement

Participants express multiple competing views regarding the nature of the forces involved in covalent bonding, particularly concerning the role of electromagnetic interactions and the significance of electron density. The discussion remains unresolved with no clear consensus on the explanations provided.

Contextual Notes

Limitations include varying interpretations of the electromagnetic force components and the implications of quantum mechanics on electron behavior in covalent bonds. Some assumptions about the nature of forces and interactions are not fully explored.

Anonymous Vegetable
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In a covalent bonded molecule, what is the force responsible for the molecule staying together. To my knowledge it's to do with electrons of opposite spins and being at a lower energy with valence shells filled but what is the force itself that pulls a second atom along if the atom it's bonded to is pulled?
 
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The electromagnetic interaction. Pull one nucleus, and you stretch the electron orbital a bit, the electron gets a slightly higher wavefunction amplitude between the two atoms and follows the pulled nucleus partially, that also let's the second nucleus follow.
That is a very classical description, but it works surprisingly well.
 
Anonymous Vegetable said:
To my knowledge it's to do with electrons of opposite spins and being at a lower energy with valence shells filled
H2+ is a counterexample to that. The bond comes in the first place because the electron(s) forming the bond get to interact with the other nucleus, and the orbital spreads over both nuclei, lower the electron's energy. The presence of electron density in between the nuclei also helps reduce their Coulomb repulsion.
 
DrClaude said:
The presence of electron density in between the nuclei also helps reduce their Coulomb repulsion.
I know that this is a common description, but I really don't like it. The force between the protons is not altered at all. You just get an attractive force between protons and electron(s) in addition.
 
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mfb said:
The electromagnetic interaction. Pull one nucleus, and you stretch the electron orbital a bit, the electron gets a slightly higher wavefunction amplitude between the two atoms and follows the pulled nucleus partially, that also let's the second nucleus follow.
That is a very classical description, but it works surprisingly well.
So now I think about it, and please correct me or point out if it's a silly comment but would this be a result of the magnetic part of the electromagnetic force?
 
I don't think it is useful to split it into components here, but it is mainly the electric part. Nothing moves very fast here.
 
mfb said:
I don't think it is useful to split it into components here, but it is mainly the electric part. Nothing moves very fast here.
In that case, I'm still not quite understanding how the bonded electrons enable each other to follow one another due to the electromagnetic force.
 
Which part of post 2 is unclear?
 
mfb said:
Which part of post 2 is unclear?
The idea that a bond between two negative charges consists of electromagnetic interaction.
 
  • #10
The bond is not between two electrons. The bond is between the atoms, due to the attraction of electrons and nuclei.
 
  • #11
Covalent bonding is a quantum mechanical effect. In a bond, the electrons have more space to move than in the field of a single atom. By the uncertainty principle, this reduces their momentum and thence also their kinetic energy.
 
  • #12
DrDu said:
Covalent bonding is a quantum mechanical effect. In a bond, the electrons have more space to move than in the field of a single atom. By the uncertainty principle, this reduces their momentum and thence also their kinetic energy.
So how does the electromagnetic force come into this explanation sorry, if that's the force responsible?
 
  • #13
The electromagnetic force is the interaction that holds everything together. It let's a nucleus attract electrons (and electrons attract nuclei).
 
  • #14
mfb said:
The electromagnetic force is the interaction that holds everything together. It let's a nucleus attract electrons (and electrons attract nuclei).
So would it be valid, to an extent to think of it in this sequence? Electron orbitals overlap forming larger area of electron density. Both nuclei are simultaneously attracted to this area holding the molecule together.
 
  • #15
Anonymous Vegetable said:
So would it be valid, to an extent to think of it in this sequence? Electron orbitals overlap forming larger area of electron density. Both nuclei are simultaneously attracted to this area holding the molecule together.

As a first approximation it sounds OK to me. Note, that it doesn't require any magnetic part, just electrostatic attraction.
 
  • #16
Borek said:
As a first approximation it sounds OK to me. Note, that it doesn't require any magnetic part, just electrostatic attraction.
I realize that now sorry, the guess at magnetic involvement was more a wild guess because the word spin was mentioned.
 
  • #17
Anonymous Vegetable said:
So how does the electromagnetic force come into this explanation sorry, if that's the force responsible?
Of course it is. The attraction by the nuclei forms the basin in which the electrons are moving.
 

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