Bond Angles for H2O

(Polar molecules, Non-polar molecules, etc.)

Moderators: Chem_Mod, Chem_Admin

804991762_4A
Posts: 47
Joined: Fri Apr 06, 2018 11:04 am

Bond Angles for H2O

Postby 804991762_4A » 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?

Yvonne Du
Posts: 64
Joined: Fri Sep 28, 2018 12:23 am

Re: Bond Angles for H2O

Postby Yvonne Du » 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.

Rhea Churi 4K
Posts: 62
Joined: Fri Sep 28, 2018 12:28 am

Re: Bond Angles for H2O

Postby Rhea Churi 4K » 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.

Celeste 1I
Posts: 44
Joined: Fri Sep 28, 2018 12:18 am

Re: Bond Angles for H2O

Postby Celeste 1I » 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.

uhedlund
Posts: 38
Joined: Wed Nov 15, 2017 3:03 am

Re: Bond Angles for H2O

Postby uhedlund » Sun Nov 18, 2018 10:49 pm

The lone pairs result in a decrease in the size of the angle .

Sheridan Slaterbeck 1J
Posts: 62
Joined: Fri Sep 28, 2018 12:27 am

Re: Bond Angles for H2O

Postby Sheridan Slaterbeck 1J » 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

Nicole Garrido 2I
Posts: 52
Joined: Fri Sep 28, 2018 12:18 am

Re: Bond Angles for H2O

Postby Nicole Garrido 2I » 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.

duenezjuleny1D
Posts: 48
Joined: Fri Sep 28, 2018 12:24 am

Re: Bond Angles for H2O

Postby duenezjuleny1D » Sun Nov 18, 2018 11:02 pm

it is because of the lone pair electrons they will repel each other and change the angels

Andrew Lam 3B
Posts: 30
Joined: Fri Sep 28, 2018 12:24 am

Re: Bond Angles for H2O

Postby Andrew Lam 3B » 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.


Return to “Determining Molecular Shape (VSEPR)”

Who is online

Users browsing this forum: No registered users and 2 guests