What is the hybridization state of the central nitrogen atom in an ammonia molecule, and what is its resulting molecular geometry?

💡 Solution & Explanation

In an ammonia molecule, the central nitrogen atom forms three single sigma bonds with hydrogen atoms and retains one lone pair of electrons, resulting in four electron pairs arranged in an sp3 tetrahedral electronic geometry. The presence of the lone pair repels the bonding pairs slightly, distorting the shape into a trigonal pyramidal geometry with a bond angle of approximately 107 degrees. Trigonal planar geometry corresponds to sp2 hybridization without lone pairs like boron trifluoride. Lone pair-bond pair repulsion explains why ammonia deviates from the ideal tetrahedral angle of 109.5 degrees.