Question

Which statements are NOT TRUE about $XeO_2F_2$?
A. It has a see-saw shape.
B. Xe has 5 electron pairs in its valence shell in $XeO_2F_2$.
C. The O-Xe-O bond angle is close to $180^\circ$.
D. The F-Xe-F bond angle is close to $180^\circ$.
E. Xe has 16 valence electrons in $XeO_2F_2$.

• A. B and D Only
• B. B, C and E Only
• C. A and D Only
• D. B, D and E Only

Hint:

In TBP geometry, Lone Pairs and Double Bonds prefer equatorial positions to minimize repulsion. Axial bonds are longer/weaker.

Answer 1

The Correct Option is B

To determine which statements are NOT TRUE about XeO_2F_2, let us evaluate each statement individually:

1. Statement A: It has a see-saw shape.

   Explanation: The molecule XeO_2F_2 has xenon (Xe) as the central atom. In this molecule, xenon is surrounded by two oxygen atoms and two fluorine atoms, with one lone pair, making the geometry around xenon a trigonal bipyramidal arrangement. The lone pair occupies one equatorial position, resulting in a see-saw shape. Therefore, Statement A is TRUE.

2. Statement B: Xe has 5 electron pairs in its valence shell in XeO_2F_2.

   Explanation: Xenon originally has 8 valence electrons. In XeO_2F_2, xenon forms bonds with two oxygen atoms and two fluorine atoms, utilizing 4 electron pairs for these bonds. Additionally, there is one lone pair of electrons remaining on the xenon. Thus, xenon indeed has 5 electron pairs (4 bonding pairs + 1 lone pair) in its valence shell, making Statement B TRUE.

3. Statement C: The O-Xe-O bond angle is close to 180^\circ.

   Explanation: In a see-saw shape, the O-Xe-O bond angle does not reach 180^\circ due to the repulsion between the lone pair and the bonding pairs which reduces this angle. Typically, this angle is less than 120^\circ. Thus, Statement C is FALSE.

4. Statement D: The F-Xe-F bond angle is close to 180^\circ.

   Explanation: In the see-saw molecular shape, the axial F-Xe-F bond angle could achieve close to 180^\circ due to the linear arrangement of atoms along the axial positions. Thus, Statement D can be considered TRUE.

5. Statement E: Xe has 16 valence electrons in XeO_2F_2.

   Explanation: Xenon (Xe) has 8 valence electrons. The count of valence electrons in XeO_2F_2 is determined by the formula alone based on the initial valence of Xe and the bond formations, not additional electrons. The eight electrons form bonds or remain as lone pairs. Thus, the presence of 16 valence electrons is not accurate. Therefore, Statement E is FALSE.

Based on the above evaluations, Statements C and E are FALSE. This confirms that the correct option for statements that are NOT TRUE is: B, C and E Only.