Question

question 66 (1 point)
nh₃ molecule has __type of electron geometry and __type of molecular geometry.

1. trigonal pyramid, trigonal pyramid
2. tetrahedral, trigonal (triangular) pyramid
3. tetrahedral, tetrahedral
4. tetrahedral, trigonal planar

Explanation:

To determine the electron and molecular geometry of \( \text{NH}_3 \) (ammonia), we analyze the central nitrogen atom:

• Electron Geometry: Nitrogen has 5 valence electrons. In \( \text{NH}_3 \), it forms 3 single bonds with hydrogen atoms and has 1 lone pair of electrons. The total number of electron domains (bonding + lone pairs) is \( 3 + 1 = 4 \). For 4 electron domains, the electron geometry is tetrahedral (based on VSEPR theory, where 4 domains correspond to a tetrahedral arrangement).
• Molecular Geometry: Molecular geometry considers only the bonding regions (ignoring lone pairs). With 3 bonding pairs and 1 lone pair, the 3 hydrogen atoms form a triangular pyramid (trigonal pyramid) around the nitrogen atom. The lone pair repels the bonding pairs, causing the bond angles to be less than the ideal tetrahedral angle, resulting in a trigonal (triangular) pyramid molecular geometry.

Now, we match this to the options:

• Option 1: Incorrect (electron geometry is not trigonal pyramid).
• Option 2: Correct (electron geometry = tetrahedral, molecular geometry = trigonal pyramid).
• Option 3: Incorrect (molecular geometry is not tetrahedral).
• Option 4: Incorrect (molecular geometry is not trigonal planar).

Answer:

1. Tetrahedral, Trigonal (triangular) Pyramid