Why Is the Angle Between Hydrogen Atoms in Water Molecules 105 Degrees?

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In summary, Richard Feynman discusses in "Six Easy Pieces", Chapter 1, the angle between hydrogen atoms in a water molecule, which is 105 deg. This is due to the VSEPR theory, which explains that the free and bound electron pairs in H2O try to arrange in a tetrahedral configuration. However, since the bound electron pairs extend over two atoms, the angle between them is slightly smaller than the ideal tetrahedral angle of 109.5 deg. It is likely that Feynman found this angle interesting or illuminating, and John is seeking clarification on why this angle is 105 deg and if it would be the same for a heavy water molecule.
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johnhb
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In "Six Easy Pieces", Chapter 1, Richard Feynman discusses how the angle between hydrogen atoms in a water molecule is 105 deg. Why is this? Would it be the same for a heavy water molecule?

John
 
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Probably Feynman discussed it because he found it interesting or illuminating!
 
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Thank you, Dr.Dru, but I was wondering why the angle is 105 deg?

John
 
  • #4
Yes, but what is the problem? I thought Feynman gave an explanation. Is there anything unclear with his explanation?
One of the easiest explanations is the VSEPR (Valence Shell Electron Pair Repulstion) theory.
According to it the free and bound electron pairs repell each other. In H2O there are two free electron pairs and two bound ones, hence they try to arange in a tetrahedral configuration.
The bound electron pairs extend over two atoms, hence the repulsion between them is a little bit smaller whence the angle between the bound pairs is a little bit smaller than 109.5 deg, the ideal tetrahedral angle.
 

1. What is the angle between H in H2O?

The angle between H in H2O is approximately 104.5 degrees.

2. How is the angle between H in H2O determined?

The angle between H in H2O is determined by the arrangement of the atoms in the water molecule and the repulsion of the electron pairs in the molecule.

3. Can the angle between H in H2O change?

The angle between H in H2O can vary slightly due to external factors such as temperature and pressure, but it typically remains close to 104.5 degrees.

4. What is the significance of the angle between H in H2O?

The angle between H in H2O is important in determining the shape and properties of the water molecule, which in turn affects its ability to form hydrogen bonds and its overall chemical behavior.

5. How does the angle between H in H2O compare to other molecules?

The angle between H in H2O is relatively small compared to other molecules, as most molecules have bond angles greater than 104.5 degrees. This unique angle in water contributes to its many unique properties.

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