Vsepr Theory And Shape Of Molecules

The question asks to identify the incorrect geometry among the listed molecules based on their electron geometry.

1. Step 1: Understand the molecular shapes. - BrF : The molecule has 5 fluorine atoms attached to a central bromine atom, with one lone pair of electrons on the bromine. According to the VSEPR theory, BrF adopts an octahedral geometry, not trigonal bipyramidal. Therefore, the statement for BrF is incorrect. - SF : This molecule adopts a see-saw geometry due to 4 bonding pairs and one lone pair of electrons on sulfur, which is correct. - NH : Ammonia adopts a pyramidal shape due to 3 bonding pairs and one lone pair of electrons on nitrogen, which is correct. - XeF : Xenon tetrafluoride has a square planar geometry because it has 4 bonding pairs and 2 lone pairs of electrons, making the geometry planar, which is correct. Thus, the incorrect geometry is for BrF , and the correct geometry is octahedral.

Step 1: Understanding the structure.
XeF has a square planar structure due to the presence of two lone pairs of electrons on the central xenon atom. This gives a total of four bonds, forming a square planar geometry.

Step 2: Analyzing the options.
- (A) XeF has a square planar structure with two lone pairs on the xenon atom.
- (B) NiF has a tetrahedral structure, not planar, with no lone pairs on the central atom.
- (C) SF has a seesaw structure with one lone pair.
- (D) SF has an octahedral structure with no lone pairs.

Step 3: Conclusion.
The correct answer is (A), as XeF has a square planar structure with two lone pairs.

Step 1: Understanding the Concept:
According to the Valence Shell Electron Pair Repulsion (VSEPR) theory, the geometry of a molecule depends on the total number of electron domains around the central atom.
Step 2: Key Formula or Approach:
The approach uses VSEPR rules where Steric Number = (Number of Bond Pairs) + (Number of Lone Pairs). Minimizing lone-pair repulsions defines the final molecular shape.
Step 3: Detailed Explanation:
The molecule has the generic formula .
It possesses 3 bond pairs (B) and 2 lone pairs (E), making a total of 5 electron domains.
With 5 electron domains, the central atom undergoes hybridization.
The basic electron domain geometry for 5 domains is trigonal bipyramidal.
To minimize repulsion (especially lone pair-lone pair and lone pair-bond pair repulsions), the lone pairs occupy the more spacious equatorial positions.
The three bond pairs occupy the remaining two axial positions and one equatorial position.
The resulting molecular geometry, observing only the atoms and ignoring the lone pairs visually, takes the shape of the letter 'T'.
Therefore, the molecular geometry is T-shaped.
Step 4: Final Answer:
The molecular geometry is T-shaped.