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Refreshing General Chemistry Why Review General Chemistry? Molecular Geometry

Molecular Geometry

Estimated reading time: 1 min

In this chapter
In this section

Topics

  • VSEPR theory
  • Molecular shape
  • Bond angles

What to Focus On

Focus on the geometries that appear most often in organic chemistry: tetrahedral (four groups around carbon), trigonal planar (three groups, as in a double bond), linear (two groups, as in a triple bond), bent (as in water, where two lone pairs compress the bond angle), and trigonal pyramidal (as in amines, where one lone pair does the same).

Figure II.1. VSEPR geometries by number of electron domains and lone pairs: linear, trigonal planar, bent/angular, tetrahedral, and trigonal pyramidal — the shapes that recur throughout organic chemistry. ("VSEPR molecular geometries" by OpenStax, CC BY 4.0, via Chemistry LibreTexts.)
Figure II.1. VSEPR geometries by number of electron domains and lone pairs: linear, trigonal planar, bent/angular, tetrahedral, and trigonal pyramidal — the shapes that recur throughout organic chemistry. ("VSEPR molecular geometries" by OpenStax, CC BY 4.0, via Chemistry LibreTexts.)

Lone pairs are worth special attention. They affect shape, but they also make atoms like oxygen and nitrogen reactive as nucleophiles — a concept that reappears throughout the course.

Why It Matters

Organic chemistry is inherently three-dimensional.

Shape determines properties and reactivity.

Reading

OpenStax Chemistry 2e

Videos

Gentle Exercises

Predict the geometry of:

  • CH₄
  • NH₃
  • H₂O
  • CO₂