How do I determine the hybridization and bonding in ammonia?

1 Answer
Ernest Z.
Jun 22, 2017

Here's how to do it.

Explanation:

You draw the Lewis structure (Step 1) and use VSEPR theory to determine its electron domain geometry as tetrahedral and its molecular shape (Step 2) as a trigonal pyramid.

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Then you consult a table like the one below.

Hybridization
(Adapted from SlideShare)

You find that the #"N"# atom uses #"sp"^3# orbitals, so you draw four tear-drop shapes pointing towards the corners of a tetrahedron (Step 3).

The #"H"# atoms use their #"1s"# orbitals for bonding, so you draw small circles intersecting with three of the #"sp"#3 orbitals.

That shows that the #"N-H"# bonds are σ bonds formed by the overlap of #"sp"^3# orbitals of #"N"# and #"1s"# orbitals of #"H"#.

However, the molecular orbitals include both the #"N"# and #"H"# nuclei.

NH3

In the diagram above, the bond-line drawing shows that the #"H"# nuclei are completely inside the larger teardrop-shaped #"sp"^3"-s"# σ molecular orbitals.

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