Chemistry Chemical Bonding PMC 2021
PMDC Verified Question 62 of 102
The geometry of \( \text{AB}_3 \) type molecule is:
A
Trigonal pyramidal
B
Trigonal planar
C
Trigonal bipyramidal
D
Tetragonal
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option B: Trigonal planar
Concept:

According to VSEPR theory, a central atom bonded to three identical atoms with zero lone pairs will arrange those bonds to maximize distance and minimize repulsion.

Formula:

$$ \text{Bond Angle} = \frac{360^{\circ}}{3} = 120^{\circ} $$

Solution:

  • Three electron domains will space themselves out equally in a two-dimensional plane.


  • This results in a flat, triangular shape known as Trigonal Planar geometry (e.g., \( \text{BF}_3 \)).


Why other options are incorrect:

  • Option A: Trigonal pyramidal occurs when a lone pair pushes the three bonds down into a 3D pyramid (\( \text{AB}_3\text{E} \)).
  • Option C: Requires 5 bond pairs (\( \text{AB}_5 \)).

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