Understanding the Properties of Water at 104.45°

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Discussion Overview

The discussion revolves around the molecular geometry of water, specifically addressing why the bond angle is measured at 104.45° instead of the expected 109.47°. The scope includes theoretical explanations related to hybridization and electron pair repulsion.

Discussion Character

  • Technical explanation, Conceptual clarification, Debate/contested

Main Points Raised

  • One participant suggests that the bond angle of water is due to the sp3 hybridization of the oxygen atom and the greater repulsion from non-bonding electron pairs compared to bonding pairs.
  • Another participant acknowledges this explanation but points out that it does not fully account for the divergence from the expected bond angle, referencing an external source for further context.
  • A different viewpoint is presented that attributes the smaller bond angle to the delocalization of lone pairs and proposes that the 2s orbital may be unhybridized, suggesting a steric repulsion effect from hydrogen atoms as a contributing factor.

Areas of Agreement / Disagreement

Participants express differing views on the reasons behind the bond angle of water, indicating that multiple competing explanations exist without a clear consensus.

Contextual Notes

Limitations include potential missing assumptions regarding hybridization and electron repulsion, as well as the dependence on specific definitions of orbital hybridization.

msadoti
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Why does water angled 104.45° ?
 
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Because the O-atom is sp3 hybridized, and the repulsion from non-bonding electron pairs is greater than that from bonding electron pairs.
 
Gokul - good answer. But it doesn't totally explain the divergence of the 104.45 degree angle from the expected 109.47 degree angle - this explains why (I think):

http://xnet.rrc.mb.ca/rcharney/The%20water%20molecule.htm
 
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Jim, the divergence was traditionally explained in terms of a greater delocalization of the lone pairs causing the bond angle to be smaller that the symmetric angle - this is what I stated above. However, the information in your reference suggests there is now good reason to believe that in fact, the 2s orbital is unhybridized and the 105 deg = 90 deg + steric repulsion from H atoms.

Thanks for the link.
 

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