Difference ionic and covalent bonds

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Discussion Overview

The discussion revolves around the differences between ionic and covalent bonds, exploring their definitions, characteristics, and the nuances of their existence. Participants engage in a conceptual examination of bond types, referencing quantum mechanics and chemical theory.

Discussion Character

  • Conceptual clarification
  • Debate/contested
  • Technical explanation

Main Points Raised

  • One participant notes that while chemistry books define ionic and covalent bonds as distinct, the wave functions of electrons are spread around both nuclei, leading to confusion about the meaning of ionic bonds.
  • Another participant asserts that perfectly ionic bonds do not exist.
  • A different viewpoint suggests that bonds exist on a spectrum between covalent and ionic, with pure covalent bonds only occurring between identical atoms, and the degree of ionic character varying in other cases.
  • One participant expresses difficulty finding a quantum theory of the ionic bond, implying skepticism about its existence.
  • Another participant references Linus Pauling's work, suggesting that potential energy curves can illustrate the ionic and covalent nature of bonds, even for equal atoms, and describes how these curves behave at different distances.

Areas of Agreement / Disagreement

Participants express differing views on the existence and nature of ionic and covalent bonds, indicating that multiple competing perspectives remain without a consensus on the definitions or characteristics of these bonds.

Contextual Notes

Participants highlight limitations in the definitions and understanding of ionic bonds, noting the dependence on quantum mechanics and the ambiguity in distinguishing between bond types based on electron sharing.

jostpuur
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According to chemistry books the ionic and covalent bonds are a different thing. In covalent bonds the electrons share the same space around the bound nuclei, while in ionic bonds two ions are bound by the electric force between the ions.

However, the truth is that the wave functions of the electrons are spread onto the surroundings of the both nuclei anyway, and I'm left unable to understand what the ionic bond is supposed to mean.
 
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My understanding is that you never get bonds that are perfectly ionic.

Claude.
 
It is a question of degree. Pure covalent bonds can only exist between identical atoms (such as a homonuclear diatomic molecule), while one could argue a long time whether pure ionic bonds can exist. [Edit: the other Claude was faster than me on this last point.]

For most molecules, a bond will be somewhere between covalent and ionic. When the sharing is more or less equal, then we call that a covalent bond; when it is very unequal, ionic. In QM (LCAO-MO), you would call a bond ionic if the corresponding bonding orbital leads to a much greater probability density of the electron around one nucleus than the other.
 
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I've consulted several textbooks looking for 'quantum theory of the ionic bond' (let's say in CsF). Turned up nothing. So I'm assuming that the 'ionic bond' doesn't exist.

EDIT: Just saw post #3.
 
You could have a look in Linus Pauling "The nature of the chemical bond"
Usually you can draw two potential energy curves, even for bonds between equal atoms.
One of the curves is predominantly ionic, the other one covalent.
At large distances, the ionic rises like 1/R and lies above the covalent one. In molecules which are
covalent at the equilibrium distance, the ionic curve lies always above the ionic one, in those molecules which are
predominantly ionic at equilibrium distances, the two curves nearly intersect at some larger distance.
There are pictures in Paulings book and good explanations.
 

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