Geometry in BeCl₂ & BF₃: A VSEPR Theory Perspective

The video tutorial explains the classification of molecules based on the presence of lone electron pairs on the central atom. It introduces the general formula ABX, where A is the central atom and X is the number of B atoms attached. The tutorial predicts the shapes of AB2 and AB3 molecules, using beryllium chloride and boron trifluoride as examples. AB2 molecules like beryllium chloride have a linear shape with a bond angle of 180°, while AB3 molecules like boron trifluoride have a trigonal planar shape with a bond angle of 120°.

What is the general formula used to describe molecules with a central atom and attached groups?

• XYZ

• LMN

• ABX

• CDE

In a molecule with the formula AB2, what is the typical shape and bond angle?

• Tetrahedral, 109.5°

• Linear, 180°

• Trigonal planar, 120°

• Bent, 104.5°

Which molecule is used as an example of an AB2 type in the video?

• Methane

• Boron trifluoride

• Water

• Beryllium chloride

What is the geometry of an AB3 type molecule like boron trifluoride?

• Linear

• Trigonal planar

• Tetrahedral

• Square planar

What is the bond angle in a trigonal planar molecule like BF3?

• 180°

• 90°

• 109.5°

• 120°