Beginner Topic 158 of 1102 Bonding & Molecular Structure
Bent Geometry
Angular shape caused by lone pairs, as in water and SO2.
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In-depth explanation of Bent Geometry
Bent or angular geometry arises when a central atom has two bonds together with one or two lone pairs. Lone pairs repel the bonds more strongly than bonds repel each other, pushing the bond angle below the ideal value for the electron geometry. A tetrahedral arrangement with two lone pairs gives an angle near 104.5 degrees in water, while a trigonal planar arrangement with one lone pair gives an angle near 119 degrees in sulfur dioxide. Bent molecules are polar because their bond dipoles do not cancel. Water and sulfur dioxide are the classic examples.
Going deeper: Bent Geometry
Key ideas: Two sources: AX2E (SO2, O3, NO2-, about 117 to 119 degrees) and AX2E2 (H2O 104.5, H2S 92, OF2 103). Angles shrink down a group as the central atom becomes larger and less hybridized: H2S has near 92 degrees with almost pure p orbitals. NO2 with one unpaired electron has a larger angle of 134 degrees.
Common mistakes and connections: Students give 109.5 degrees for all bent molecules or 120 for all of the other type, ignoring lone pair effects. Another is saying bent molecules are always nonpolar if they look symmetric. They are polar because the dipoles add. Connects to VSEPR deviations, hybridization of water and Bent's rule.
Visualization of Bent Geometry
Sulfur dioxide has two bonds and one lone pair on sulfur, which bends the molecule to about 119 degrees. The interactive lesson shows this as a live animation or chart.
Worked example and use case
Water has an H-O-H angle of 104.5 degrees and sulfur dioxide has an O-S-O angle of about 119 degrees.
Frequently asked questions about Bent Geometry
What is Bent Geometry?
Angular shape caused by lone pairs, as in water and SO2.
Is Bent Geometry a beginner, intermediate or advanced topic?
Bent Geometry is a beginner topic in Bonding & Molecular Structure. It needs no earlier chemistry lessons and is a good starting point.
What should I learn before Bent Geometry?
Study these earlier topics in Bonding & Molecular Structure first: Tetrahedral Geometry, Trigonal Bipyramidal Geometry, Octahedral Geometry.
What comes after Bent Geometry?
The next topics in Bonding & Molecular Structure are Trigonal Pyramidal Geometry and See-Saw Geometry.
Can I practise Bent Geometry with quizzes?
Yes. The interactive lesson includes a self-check question on Bent Geometry, and the Bonding & Molecular Structure quiz draws on every topic in this area.
Where Bent Geometry fits in Bonding & Molecular Structure
Bent Geometry is topic 43 of 104 in Bonding & Molecular Structure.