Provide the Lewis structure and molecular geometry as predicted by VSEPR (with solution) of
the following:
(a) Xenon dichloride, XeCl2
The correct answer and explanation is :
Lewis Structure and Molecular Geometry of Xenon Dichloride (XeCl₂)
Step 1: Determine the Total Valence Electrons
- Xenon (Xe) is a noble gas in Group 18 with 8 valence electrons.
- Chlorine (Cl) is in Group 17, and each chlorine atom has 7 valence electrons.
- Since there are two chlorine atoms, their total contribution is 2 × 7 = 14 valence electrons.
- The total number of valence electrons in XeCl₂ is:
[
8 + 14 = 22 \text{ valence electrons}
]
Step 2: Draw the Skeletal Structure
- Xenon (Xe) is the central atom because it is the least electronegative element.
- Two chlorine (Cl) atoms are attached to Xe via single bonds.
- Each single bond accounts for 2 electrons, so 2 × 2 = 4 electrons are used for bonding.
- The remaining 22 – 4 = 18 electrons are placed as lone pairs on Xe and Cl.
Step 3: Assign Lone Pairs
- Each Cl needs 8 valence electrons (octet rule). Since each Cl is already bonded to Xe (2 electrons), it needs 6 more electrons as lone pairs.
- Placing 3 lone pairs (6 electrons) on each Cl satisfies their octet.
- After assigning 6 electrons to each Cl, 6 electrons remain, which are placed as three lone pairs on Xe.
Thus, the Lewis structure of XeCl₂ consists of:
- Xenon (Xe) at the center with three lone pairs.
- Two chlorine (Cl) atoms each having three lone pairs.
Step 4: Determine Molecular Geometry Using VSEPR Theory
- Electron domains: Xenon has five electron domains (two bonding pairs and three lone pairs).
- VSEPR Shape Prediction:
- According to the AX₂E₃ notation, XeCl₂ adopts a linear molecular geometry because lone pairs arrange themselves to minimize electron repulsion.
- The lone pairs on Xe are positioned equatorially, and the bonding pairs (Cl-Xe-Cl) are positioned axially in a trigonal bipyramidal electron geometry, but the molecular shape is linear.
Final Answer:
- Lewis Structure: Xe with three lone pairs and single bonds to two Cl atoms.
- Molecular Geometry: Linear (bond angle ≈ 180°).