NH3 Lewis Structure
The Lewis dot structure of ammonia (NH3): nitrogen in the centre with a single bond to each hydrogen and one lone pair, giving a trigonal pyramidal shape.
How to draw the Lewis structure of NH3
- Count valence electrons: N has 5, each H has 1, so the total is 5 + 1 + 1 + 1 = 8 electrons.
- Put nitrogen in the centre and join each hydrogen with a single bond (6 electrons used).
- Place the remaining 2 electrons as one lone pair on nitrogen. Nitrogen now has 3 bonds + 1 lone pair = 8 electrons, and each hydrogen has 2.
Worked example: counting electron domains
Nitrogen has 4 electron domains (3 bonding pairs, 1 lone pair), so the electron geometry is tetrahedral. Molecular shape only counts the atoms, so removing the lone pair from the picture leaves a trigonal pyramidalshape with a bond angle of about 107°.
Compare it with the H2O Lewis structure (2 bonds, 2 lone pairs, bent) and check any shape on the VSEPR chart, then build NH3 in 3D in the Molecule Builder.
Frequently asked questions
How many valence electrons does NH3 have?
Eight. Nitrogen has 5 and each hydrogen has 1, so 5 + 1 + 1 + 1 = 8 valence electrons.
Why is NH3 trigonal pyramidal and not trigonal planar?
Nitrogen has four electron domains: three bonds to hydrogen and one lone pair. The lone pair still takes up space and pushes the three N-H bonds down, giving the molecule a pyramid shape with nitrogen at the apex.
What is the bond angle in NH3?
About 107°, slightly less than the 109.5° of a perfect tetrahedron, because the lone pair on nitrogen pushes the three bonding pairs closer together.
Is NH3 polar or nonpolar?
Polar. Nitrogen is more electronegative than hydrogen, and the pyramidal shape means the bond dipoles and the lone pair do not cancel out, leaving the nitrogen end slightly negative.
