[nyasha]

Arrange H-S-H ,H-N-H, H-O-H and H-S-H bond angles in order of tightest to widest.



My attempt to solution:


1. H-S-H
2.H-O-H
3.H-N-H
4.H-C-H

( Is this correct ? I am confused because it seems as if most of them make a 109.5°)

[Arkcon]

Hmmm... H-N-H and H-C-H, those don't actually exist, is that really what the question is asking for?  If so, consider what you'd have to do to make them exist, and how that would affect bond angle.

[ARGOS++]

Dear nyasha;

Additional to Arkcon think about the bond angels of H₂S and H₂O, because they are "enough" different to 109.5°!!   -  Otherwise ask Wiki for.

Good Luck!
                    ARGOS⁺⁺

[nyasha]

Thanks very much for the help. The notes l were using had a an error. I consulted with a chemistry textbook and figured out that H-S-H has 92°, H-O-H has 104.5°, H-N-H 107° and H-C-H has 109.5°

[ARGOS++]

Dear nyasha;

You are right, if you see H-N-H and H-C-H as a part of a molecule.

You 're welcome!   ─   Soon again.
Good Luck!
                    ARGOS⁺⁺

[macman104]

The real question is can you explain why those angles are observed?

[nyasha]

The real question is can you explain why those angles are observed?

Well those angles are observed because of VSPER theory and lone electron pairs.

[macman104]

Haha, right you are.  I more meant, are you able to explain why (using VSPER and lone electron pair information) that H-S-H has a smaller angle than H-O-H, etc...

I think that is the a good exercise in making sure you understand these topics.

[nyasha]

Haha, right you are.  I more meant, are you able to explain why (using VSPER and lone electron pair information) that H-S-H has a smaller angle than H-O-H, etc...

I think that is the a good exercise in making sure you understand these topics.

Doesn't it also have something to do with hybridization ?

[macman104]

Not quite.  They are all sp3 hybridized.  But it does have to do with electron pairs and the size of the shells.

Compare:  H-S-H and H-O-H.  Both have two lone pairs of electrons, but there is one difference between the elements S and O, that causes H-S-H to be smaller.

Compare:  H-O-H and H-N-H.  In something like NH₃ and H₂, which one has more lone pairs of electrons.  How might this affect the bond angles experienced?

Also, I'm pretty sure the question did not mean to imply H-N-H and H-C-H existed, but in something like NH₃ and CH₄.

[ARGOS++]

Dear macman104;

I don’t fully agree with you!: -
Because for H-C-H  a sp² hybridisation is not only thinkable as for Ethylene wit 117°C:

http://en.wikipedia.org/wiki/Ethylene

Good Luck!
                    ARGOS⁺⁺

[macman104]

Correct, but I imagine for the purposes of this question, we are considering these single bonded molecules, such as CH₄.  For this question, that is really the only adequate way to compare these bond angles.  Do you disagree?

[ARGOS++]

Dear macman104;

For the original question I don’t disagree with you!

But the last question from nyasha asked about "different" hybridisation, and in this moment the sp² hybridisation should also be included to be fair.

Good Luck!
                    ARGOS⁺⁺