Shape of hydrogen selenide.

In summary, H2Se has a bent shape because of the arrangement of its valence electrons. This prevents the bond angle from being 180°.
  • #1
coconut62
161
1
Why does H2Se have a bent shape?

It has 6 valence electrons. 2 are used to bond with each of the hydrogens. 2 more up and 2 more down. So the repulsion of the lone pairs cancel off each other. Isn't this arrangement going to make the bond angle 180°?
 
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  • #2
coconut62 said:
Why does H2Se have a bent shape?

It has 6 valence electrons. 2 are used to bond with each of the hydrogens. 2 more up and 2 more down. So the repulsion of the lone pairs cancel off each other. Isn't this arrangement going to make the bond angle 180°?

The repulsive forces between the lone pairs is greater than the forces between the 2 bonding pairs so the bonding pairs get pushed closer to increase the distance between the 2 lone pairs.

Another way to look at it is that molecules with 4 pairs of electrons form a tetrahedral shape, think methane, except in molecules like H2O or H2Se, 2 of the corners do not have another atom but they do have an electron pair.
 
  • #3
trollcast said:
The repulsive forces between the lone pairs is greater than the forces between the 2 bonding pairs so the bonding pairs get pushed closer to increase the distance between the 2 lone pairs..

Push closer to where? If the two lone pairs are arranged at 180° to each other and so does the bond pairs, then maximum distance will be achieved, no?
 
  • #4
coconut62 said:
Push closer to where? If the two lone pairs are arranged at 180° to each other and so does the bond pairs, then maximum distance will be achieved, no?

http://www.elmhurst.edu/~chm/vchembook/images/206water.gif [Broken]

Try looking at that and see how the arrangement of the bonds and electron pairs maximises the distances between them (I think you are maybe only thinking about moving them round in the same plane)

I know the diagram says water but H2Se has the same electron geometry just the angles and lengths are a bit different.

Ps. The perspective of that diagram isn't great since it appears the lone pairs are closer together than the bonding pairs but in reality the bonding pairs should be closer but it should show the sort of 3d arrangement of the pairs around the central atom.
 
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  • #5


The shape of a molecule is determined by the arrangement of its atoms and the distribution of its valence electrons. In the case of hydrogen selenide (H2Se), it has a bent shape because of the repulsion between the lone pairs of electrons on the selenium atom. The valence shell electron pair repulsion (VSEPR) theory states that electron pairs in a molecule will arrange themselves in a way that minimizes repulsion. In the case of H2Se, the two lone pairs on the selenium atom repel each other and cause the hydrogen atoms to be pushed closer together, resulting in a bent shape with a bond angle of approximately 90 degrees. This arrangement allows for the electrons to be as far apart as possible, reducing the overall repulsion and stabilizing the molecule. Therefore, the bent shape of H2Se is a result of the repulsion between the lone pairs of electrons, following the principles of VSEPR theory.
 

1. What is the shape of hydrogen selenide?

The shape of hydrogen selenide is bent or V-shaped. This means that the molecule has a bond angle of approximately 104.5 degrees.

2. What is the molecular formula for hydrogen selenide?

The molecular formula for hydrogen selenide is H2Se. This means that the molecule is composed of two hydrogen atoms bonded to one selenium atom.

3. Is hydrogen selenide a polar or nonpolar molecule?

Hydrogen selenide is a polar molecule. This is because the two hydrogen atoms have a slightly positive charge, while the selenium atom has a slightly negative charge.

4. What is the bond angle of hydrogen selenide?

The bond angle of hydrogen selenide is approximately 104.5 degrees. This is due to the repulsion between the two lone pairs of electrons on the selenium atom.

5. What are the physical properties of hydrogen selenide?

Hydrogen selenide is a colorless, flammable gas with a pungent odor. It is slightly soluble in water and has a boiling point of -41.2 degrees Celsius. It is also highly toxic and can be corrosive to metals.

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