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### Bond Angles for H2O

Posted: Sun Nov 18, 2018 9:59 pm
In lecture, Lavelle had mentioned that the bond angle for H2O is (104.5) less than 109.5. I did not understand as to why it's less than 109.5. Can someone explain why this is?

### Re: Bond Angles for H2O

Posted: Sun Nov 18, 2018 10:02 pm
In my notes I have that since H2O has two lone pair electrons and two pairs of bonding electrons, the lone pairs make the bond angle decrease a bit.

Hope this helps.

### Re: Bond Angles for H2O

Posted: Sun Nov 18, 2018 10:03 pm
This is because the molecule is polar so the positive side (H atoms) are drawn towards negative side (O and lone pairs) making the angle smaller.

### Re: Bond Angles for H2O

Posted: Sun Nov 18, 2018 10:03 pm
its because oxygen has two lone pairs which repel each other and the atoms more than atom to atom repulsion causing a bent shape. So because the lone pairs repel the Hydrogen atoms more than each one to one other their angle becomes slightly less than 109.5.

### Re: Bond Angles for H2O

Posted: Sun Nov 18, 2018 10:49 pm
The lone pairs result in a decrease in the size of the angle .

### Re: Bond Angles for H2O

Posted: Sun Nov 18, 2018 11:00 pm
The lone pairs push the bonding pairs H-O on both sides to increase the angle between lone pair and the hydrogen oxygen bond, but this decreases the angle between the two bonding pairs to 104.5 instead of 109.5

### Re: Bond Angles for H2O

Posted: Sun Nov 18, 2018 11:01 pm
H20 has two lone pairs in order to complete the valence since 2 are being shared on each side with the hydrogens. These two lone pairs push the 2 hydrogens down because of electron repulsion. So the angle between the two hydrogens is less than 109.5. It is 104.5 because there are two lone pairs which is a lot of repulsion compared to only 1 lone pair.

### Re: Bond Angles for H2O

Posted: Sun Nov 18, 2018 11:02 pm
it is because of the lone pair electrons they will repel each other and change the angels

### Re: Bond Angles for H2O

Posted: Sun Nov 18, 2018 11:42 pm
Lone pairs take up more space than bonding pairs, so instead of 109.5 for tetrahedral you get 104.5 and bent.