The electron geometry and the molecular geometry of ammonia (NH3) are, respectively: The electron geometry and the molecular geometry of ammonia (NH3) are, respectively: tetrahedral, trigonal pyramidal. tetrahedral, tetrahedral. trigonal planar, bent. tetrahedral, bent. none of the above g
The Correct Answer and Explanation is:
The correct answer is tetrahedral, trigonal pyramidal.
Explanation:
Ammonia (NH₃) has a central nitrogen atom bonded to three hydrogen atoms, with one lone pair of electrons. To determine its electron geometry and molecular geometry, we can use the Valence Shell Electron Pair Repulsion (VSEPR) theory.
- Electron Geometry:
- The electron geometry refers to the arrangement of all electron pairs (bonding and lone pairs) around the central atom.
- In NH₃, the nitrogen atom is surrounded by three bonding pairs of electrons from the hydrogen atoms and one lone pair of electrons.
- This gives a total of four electron pairs around the nitrogen atom, and according to VSEPR theory, four electron pairs will arrange themselves in a tetrahedral geometry to minimize electron repulsion.
- Molecular Geometry:
- The molecular geometry refers to the arrangement of only the atoms (not the lone pairs) around the central atom.
- Although the electron geometry is tetrahedral, the lone pair on nitrogen pushes the three hydrogen atoms downwards, causing the molecule to adopt a trigonal pyramidal shape.
- This is because the lone pair occupies one of the tetrahedral positions, leaving the remaining three positions for bonding with hydrogen atoms. The repulsion between the lone pair and the bonding pairs is stronger than between the bonding pairs, which distorts the geometry.
Why the other options are incorrect:
- Tetrahedral, tetrahedral: This would be the case if there were no lone pairs on the central atom. However, in NH₃, the lone pair causes a distortion, resulting in a trigonal pyramidal molecular geometry, not tetrahedral.
- Trigonal planar, bent: This is incorrect because NH₃ does not have a trigonal planar electron geometry; it is tetrahedral.
- Tetrahedral, bent: This would be the case if the molecule had two lone pairs, as seen in water (H₂O). However, NH₃ only has one lone pair, leading to a trigonal pyramidal shape.
- None of the above: This is incorrect, as “tetrahedral, trigonal pyramidal” is the correct answer.
Thus, the correct description of ammonia’s geometry is tetrahedral for electron geometry and trigonal pyramidal for molecular geometry.