Trend for Bond Angles in CH4, NH3, and H2O

In this video we’ll consider the trend for the bond angles in CH4, NH3 and H2O.  The Lewis structure for each molecule show us the two dimensional arrangement of the atoms around the central atom.  It also show the lone pairs (also called unboned electron pairs).  CH4 does not have any lone pair.  NH3 has one and H2O has two.

Lone pairs occupy more space and push atoms (like Hydrogen) away.  The result is that the Hydrogen atoms are closer together and therefor the bond angle is smaller.  

If we were to rank the bond angles we would see:
CH4  (methane) bond angle=109.5
NH3 (ammonia) bond angle=107.8
H2O (water) bond angle=104.5

Bond Angle visualization done using PhET (https://phet.colorado.edu/sims/html/m...)

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