Question

Use the VSEPR theory to predict the shape of each of the following molecules:

Which molecules are Trigonal Pyramidal?
a) Ammonia (NH₃)
b) Silane (SiH₄)
c) Hydrogen Selenide (H₂Se)
d) Carbon Tetraiodide (CI₄)

Answer 1

According to the VSEPR theory, ammonia (NH₃) is the only molecule among those listed that has a trigonal pyramidal shape due to its one lone pair and three bonding pairs of electrons.

Step-by-step explanation:

Using the Valence Shell Electron Pair Repulsion (VSEPR) theory, we can predict the molecular shape of a molecule by considering the number of electron pairs, including both bonding pairs and lone pairs, around the central atom. For each of the given molecules, we need to first draw the Lewis structure, then use the VSEPR model to determine the shape.

• Ammonia (NH₃) has one lone pair and three bonding pairs of electrons, which results in a trigonal pyramidal shape.
• Silane (SiH₄) has no lone pairs and four bonding pairs, leading to a tetrahedral shape.
• Hydrogen Selenide (H₂Se) has one lone pair with two bonding pairs, resulting in a bent shape.
• Carbon Tetraiodide (CI₄) has no lone pairs and four bonding pairs, which gives it a tetrahedral shape as well.

Among these molecules, ammonia (NH₃) is the only one with a trigonal pyramidal shape according to the VSEPR theory.