Ammonia (NH3) Has Electron Pair Geometry And Respectively.
A. Tetrahedral, Trigonal Pyramidal
B. Octahedral, T-Shaped
C. Trigonal Bipyramidal, T-Shaped
D. Octahedral, Trigonal Planar
E. T-Shaped, Trigonal Planar
The correct answer and explanation is :
The correct answer is:
A. Tetrahedral, Trigonal Pyramidal
Explanation:
Ammonia (NH₃) has a central nitrogen atom (N) bonded to three hydrogen atoms (H). To determine its electron pair geometry and molecular geometry, we use VSEPR (Valence Shell Electron Pair Repulsion) theory.
1. Electron Pair Geometry: Tetrahedral
- The nitrogen atom has 5 valence electrons.
- Three of these electrons form single bonds with hydrogen atoms.
- The remaining two electrons form a lone pair.
- This makes a total of four electron domains (three bond pairs and one lone pair).
- According to VSEPR theory, four electron pairs around a central atom adopt a tetrahedral arrangement to minimize repulsions.
2. Molecular Geometry: Trigonal Pyramidal
- Even though the electron pair geometry is tetrahedral, the actual shape (molecular geometry) is determined only by the positions of atoms, not lone pairs.
- The three hydrogen atoms form a base of a pyramid, with the nitrogen atom at the top.
- The lone pair on nitrogen pushes the bonded hydrogen atoms slightly downward, resulting in a trigonal pyramidal shape.
Bond Angles & Effects of Lone Pairs:
- In an ideal tetrahedral geometry, the bond angle is 109.5°.
- However, due to lone pair-bond pair repulsion being stronger than bond-bond repulsion, the H-N-H bond angle reduces to approximately 107°.
Conclusion:
- Electron pair geometry: Tetrahedral (based on all four electron groups).
- Molecular geometry: Trigonal Pyramidal (based on only atoms).
NH₃ has a tetrahedral electron pair geometry but a trigonal pyramidal molecular shape.