Q10.94 CP - Chemistry: Molecular Nature Of Matter And Change

Question

Question: Consider the following molecular shapes:

1. Match each shape with one of the following species: ${\mathbf{XeF}}_{\mathbf{3}}^{\mathbf{+}}$,${\mathbf{SbBr}}_{\mathbf{3}}^{}$, ${\mathbf{GaCl}}_{\mathbf{3}}^{}$.
2. Which, if any, is polar?
3. Which has the most valence electrons around the central atom?

Step-by-Step Solution

Answer

a)  $\mathbf{Xe}{{\mathbf{F}}_{\mathbf{3}}}^{\mathbf{+}}$ matches with structure A, ${\mathbf{SbBr}}_{\mathbf{3}}$  matches with structure C and ${\mathbf{GaCl}}_{\mathbf{3}}$ matches with structure B.

b)${\mathbf{XeF}}_{\mathbf{3}}^{\mathbf{+}} \mathbf{and} {\mathbf{SbBr}}_{\mathbf{3}}$ are polar molecules.

c)  ${\mathbf{XeF}}_{\mathbf{3}}^{\mathbf{+}}$ has the greatest number of valence electrons.

Step 1: XeF 3 +

$\mathbf{Xe}{{\mathbf{F}}_{\mathbf{3}}}^{\mathbf{+}}$the molecule has a trigonal pyramidal geometry but due to the repulsion of lone pairs, it forms a T-shaped structure which is asymmetric and causes dipole moment, making the molecule polar.

It matches structure A. It is a polar molecule. It has 10 valence electrons around the central atom.

Step 2: SbBr 3

${\mathbf{SbBr}}_{\mathbf{3}}$has a tetrahedral geometry but due to presence of a lone pair of electrons it forms a pyramidal structure, pyramidal is asymmetric and hence dipole moment can not cancel out, and therefore the molecule will be polar.

It has a pyramidal structure. It matches with structure C. It is a polar molecule. It has 8 valence electrons around the central atom

Step 3: GaCl 3

${\mathbf{GaCl}}_{\mathbf{3}}$has a trigonal planar geometry which is symmetric and hence the dipole moments cancelled out.

It has a planar structure. It matches with structure B. It is non-polar. It has 6 valence electrons around the central atom

Step 4: Polar molecules

${\mathbf{XeF}}_{\mathbf{3}}^{\mathbf{+}} \mathbf{and} {\mathbf{SbBr}}_{\mathbf{3}}$ are polar molecules

Step 5: Most valence electrons

Xe have 8 electrons in its valence shell. Since in $\mathbf{Xe}{{\mathbf{F}}_{\mathbf{3}}}^{\mathbf{+}}$molecule, a positive charge is present therefore 7 electrons are remaining on Xe atom and Xe bonded with 3 Br atoms with sharing of 3 electrons hence the total number of electrons in its valence shell is 10.

 

 ${\mathbf{XeF}}_{\mathbf{3}}^{\mathbf{+}}$ has the greatest number of valence electrons.