VSEPR Model for Water

[Dhwani Krishnan 1G]

Why isn't H2O a linear molecule, but CO2 (for example) is? How do we know the bond angle isn't 180?

[almaochoa2D]

Because CO2 has double bonds and H2O doesn't.

[Faith Fredlund 1H]

When you draw the Lewis structures of H2O and CO2 you should see that the O in the H20 has two lone pairs of electrons, which somewhat clump together due to the repulsion of the H atoms. These electrons, in effect, cause the bent shape of the atoms. Meanwhile, the Lewis structure of CO2 shows the C double bonded to each of the Oxygens. Because the electrons are shared evenly and there are no lone pairs, the geometry is linear.

[Andrew Lam 3B]

The oxygen molecule on water has 2 lone pairs that cause the bond angle to be slightly depressed to around 109.5; this is called a bent configuration.