Why isn't ammonia symmetrical?

Answer 1

Ooh. This is fun.

Ammonia's formula is NH3.

There's 8 valence electrons to mess with.

6 for each H. So that makes a trigonal planar.

But that leaves us with 2 extra electrons.

Those get bonded too, so that makes a tetrahedral.

But since the 4th bond is only electrons, that is called a trigonal pyramidal.

Long story short, being symmetrical would mean that Ammonia is unpolar. (and it isn't.) Those 2 extra electrons make one side of the molecule more negative than the other, so it repels the electrons on the 3 H's, so it's unsymmetrical. (and polar.)

Answer 2

Ammonia (NH3) is not symmetrical because the nitrogen atom is larger than the hydrogen atoms, leading to an asymmetrical distribution of electron density around the molecule. This results in a trigonal pyramidal shape with the lone pair of electrons on nitrogen causing a slight deviation from symmetry.