Question

Draw Lewis structures for pyridine and its conjugate acid, the pyridinium ion, C5H5NH⁺. What are the hybridizations, electron domain geometries, and molecular geometries about the nitrogen atoms in pyridine and in the pyridinium ion?

a) Pyridine: sp³, Tetrahedral; Pyridinium ion: sp³, Tetrahedral

b) Pyridine: sp², Trigonal Planar; Pyridinium ion: sp³, Tetrahedral

c) Pyridine: sp², Trigonal Planar; Pyridinium ion: sp², Trigonal Planar

d) Pyridine: sp³, Tetrahedral; Pyridinium ion: sp², Trigonal Planar

Answer 1

In pyridine, the nitrogen atom is sp² hybridized with a trigonal planar geometry, whereas, in the pyridinium ion, the nitrogen is sp³ hybridized with a tetrahedral electron domain geometry and a trigonal pyramidal molecular geometry.

Step-by-step explanation:

The Lewis structures for pyridine and its conjugate acid, the pyridinium ion, depict different hybridizations, electron domain geometries, and molecular geometries for the nitrogen atoms. For pyridine, the nitrogen atom is sp² hybridized, which leads to a trigonal planar electron domain and molecular geometry.

In contrast, when pyridine accepts a proton to become the pyridinium ion, the nitrogen atom becomes sp³ hybridized with a tetrahedral electron domain geometry; however, the molecular geometry is trigonal pyramidal due to the presence of three bonded atoms and one lone pair on the nitrogen atom. Therefore, the correct answer is B) Pyridine: sp², Trigonal Planar; Pyridinium ion: sp³, Tetrahedral.