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Shapes of covalent molecules

Is this correct: when determining bond angles we use the electron geometry to define the initial bond angles and then subtract 2.5 degees for every lone pair?

So water has a tetraheral electron geometry but a linear molecular geomatry.

So the bond angle = 109.5 - 5 = 104.5

BUT it is drawn like a bent linear molecule with the above stated bond angles

Is this correct?

Another quick question is why do lone pairs reduce the bond angle by 2.5 degrees (I am not worried about the 2.5 degrees bit I would like to know why lone pairs reduce bond angles generally)

Reply 1

danhirons

Lone pairs repel more strongly than bonded pairs and therefore reduce the bond angle slightly by pushing the bond pairs of electrons slightly closer together - by roughly 2.5 degrees for each lone pair. Water has a non-linear shape by the way (not linear). It has a tetrahedral electron geometry as you have correctly stated though.

Reply 2

username459260

why do lone pairs repel and not sharing pairs

Reply 3

charco

Study Forum Helper

Original post by jsmith6131

why do lone pairs repel and not sharing pairs

They do, but not as much...

This is because the atoms that are being held to the central atom draw electron density in the bonding pairs away from the central atom.