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Chapter 9: Problem 14

(a) Boron trichloride \(\left(\mathrm{BCl}_{3}\right)\) and the carbonate ion \(\left(\mathrm{CO}_{3}^{2-}\right)\) are both described as trigonal. What does this indicate about their bond angles? (b) The \(\mathrm{PCl}_{3}\) molecule is trigonal pyramidal, while \(\mathrm{ICl}_{3}\) is T-shaped. Which of these molecules is flat?

Short Answer

Expert verified
In BCl3 and CO₃²⁻, both have trigonal planar molecular geometries, which indicates that their bond angles are equal to 120°. PCl3 has a trigonal pyramidal geometry, while ICl3 has a T-shaped geometry. Among these, ICl3 is the flat molecule as all atoms lie in the same plane.

Step by step solution

01

Determining Molecular Geometries of BCl3 and CO₃²⁻

The central atom in BCl3 is B (boron) and in CO₃²⁻ is C (carbon). Using the VSEPR (Valence Shell Electron Pair Repulsion) theory and considering the number of bonding pairs (BP) and lone pairs (LP) on the central atom, we can determine the molecular geometries. BCl3 has 3 bonding pairs (BP) and 0 lone pairs (LP) on the central atom (B). So, the VSEPR notation is AX₃, which indicates a trigonal planar geometry. CO₃²⁻ also has 3 bonding pairs (BP) and 0 lone pairs (LP) on the central atom (C). So, the VSEPR notation is AX₃, which again indicates a trigonal planar geometry.
02

Determining Bond Angles in BCl3 and CO₃²⁻

In both BCl3 and CO₃²⁻, the molecular geometries are trigonal planar, which implies that the bond angles will be equal to 120°.
03

Determining Molecular Geometries of PCl₃ and ICl₃

The central atom in PCl3 is P (phosphorus) and in ICl3 is I (iodine). Using the VSEPR theory, we can determine their molecular geometries based on their electron domains. PCl3 has 3 bonding pairs (BP) and 1 lone pair (LP) on the central atom (P), making it an AX₃E system. This gives the molecule a trigonal pyramidal geometry. ICl3 has 3 bonding pairs (BP) and 2 lone pairs (LP) on the central atom (I), making it an AX₃E₂ system. The geometry of this molecule is T-shaped.
04

Identifying the Flat Molecule

Now that we know the molecular geometries of PCl3 (trigonal pyramidal) and ICl3 (T-shaped), we can identify which of these molecules is flat. A flat molecule is one where all the atoms lie in the same plane. The trigonal pyramidal geometry of PCl₃ is not flat, as the phosphorus atom isn't in the same plane as the chlorine atoms. However, the T-shaped geometry of ICl₃ is flat, as the iodine atom, the central atom, lies in the same plane with all the chlorine atoms.

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Most popular questions from this chapter

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