Oxygen Bond Angle Increase: Reason Behind Increase?

  • Thread starter HIGHLYTOXIC
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In summary: H2O to H2S to H2Se. This is likely due to the increased electronegativity of oxygen, which pulls the two bond pairs closer to itself and decreases the distance between them, resulting in a larger bond angle.
  • #1
HIGHLYTOXIC
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If we take a look on the following compounds in the Oxygen family, the bond angle increases as we go down the group as :

H2O > H2S > H2Se

Whats the reason for this increase?

Is that :

1. Oxygen is more electronegative than the two, so it holds its lone pairs more tightly than the other two..Thus, the lone pairs are tightly bound to the oxygen atom, not free to wander about & repel the bond pair with hydrogen, therefore making the angle much larger.

OR​

2. Oxygen being more electronegative, pulls the two bond pairs close to itself, as the bond pairs move closer, the distance btw them decreases & this makes the bond angle larger.

Which of the above reason is right?

Thanks!
 
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  • #2
oxygen being electro negative..it holds the two bond pairs more tightly than the other other elements.. as the are pulled towards oxygen ,repulsion between these pairs increases.hance they posses a larger bond angle

the second one is correct
 
  • #3
I believe there is also a steric effect coming from the size of the anion. Comparing ionic radii, O(2-) < S(2-) < Se(2-). So the bond pairs (H-atoms) are closer to each other in H20 giving rise to stronger repulsion, and hence greater bond angle.
 
  • #4
The primary reason is that electronegativity decreases down the group as you go from O to S to Se. So the attraction for the two bonded pairs of electrons decreases as well. As a result, the electron pairs are not pulled as strongly by the central atom as you go down the group causing and therefore, electron pair repulsion decreases, decreasing the bond angle.

The electronegativity reason is more pronounced than the effect of increasing size of the central atom, as we were taught in class. However, size does have some role to play so we must not rule it out of our thinking completely. The second one is therefore correct and holds in general for most such bond angle predictions Highlytoxic.

Hope that helps,

Cheers
Vivek
 

1. What is the definition of oxygen bond angle increase?

Oxygen bond angle increase refers to the increase in the angle between two oxygen atoms in a molecule. This angle is measured in degrees and is a measure of the distance between the two oxygen atoms.

2. What is the reason behind the increase in oxygen bond angle?

The increase in oxygen bond angle is due to the repulsion between the electron pairs on the two oxygen atoms. The electron pairs are negatively charged and repel each other, causing the bond angle to increase.

3. How does the increase in oxygen bond angle affect the molecule's shape?

The increase in oxygen bond angle can change the molecule's shape from linear to bent or from trigonal planar to tetrahedral. This change in shape is due to the repulsion between the electron pairs, which causes the atoms to move away from each other.

4. What factors can influence the increase in oxygen bond angle?

The increase in oxygen bond angle can be influenced by the number of electron pairs around the oxygen atoms, the presence of other atoms or molecules in the vicinity, and the strength of the bonds between the atoms in the molecule.

5. Can the increase in oxygen bond angle affect the molecule's reactivity?

Yes, the increase in oxygen bond angle can affect the molecule's reactivity. A larger bond angle can result in a weaker bond between the oxygen atoms, making the molecule more reactive. This change in reactivity can also affect the molecule's chemical and physical properties.

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