Questions and Answers
What does the acronym VSEPR stand for?
Valence-shell electron-pair repulsion theory
What is the VSEPR Model used for?
To explain the 3-dimensional shape of molecules
What does VSEPR Theory state about molecular shapes?
The repulsion between electron pairs causes molecular shapes to adjust so that the valence-electron pairs stay as far away as possible.
What is an unshared pair?
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Describe a linear pair in terms of molecular geometry.
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What is a Trigonal Planar arrangement?
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What characterizes a Tetrahedral arrangement?
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What happens in a Tetrahedral arrangement with 1 pair of unshared electrons?
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How does a Tetrahedral arrangement with 2 pairs of unshared electrons differ?
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What defines a Trigonal Bipyramidal arrangement?
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Study Notes
VSEPR Theory Overview
- VSEPR stands for valence-shell electron-pair repulsion theory.
- The theory describes how the arrangement of electron pairs around a central atom determines the shape of a molecule.
VSEPR Model
- The model provides a framework for predicting the three-dimensional structure of molecules based on electron pair repulsion.
Molecular Shape Determination
- VSEPR theory emphasizes that electron pairs (bonding and lone pairs) repel each other, leading to the arrangement that maximizes their distance from each other.
Unshared Pairs
- Unshared (lone) electron pairs exert stronger repulsion than bonded pairs, influencing molecular geometry significantly by pushing bonding pairs closer together.
Linear Geometry
- A linear molecular shape consists of a central atom with two peripheral atoms, forming a straight line with a bond angle of 180 degrees.
Trigonal Planar Geometry
- In a trigonal planar arrangement, one central atom is bonded to three peripheral atoms, arranged in a plane with a bond angle of 120 degrees.
Tetrahedral Geometry
- A tetrahedral shape features one central atom bonded to four peripheral atoms, with a bond angle of 109.5 degrees.
Trigonal Pyramidal Geometry
- A trigonal pyramidal shape occurs when one of the four pairs of electrons in a tetrahedral arrangement is a lone pair. This causes the angle between the peripheral atoms to be about 107 degrees.
Bent Geometry
- In cases with two lone pairs, the shape becomes bent with a bond angle of approximately 104.5 degrees, derived from a tetrahedral structure.
Trigonal Bipyramidal Geometry
- A trigonal bipyramidal arrangement consists of a central atom bonded to five peripheral atoms, with bond angles of 120 degrees in the equatorial plane and 90 degrees in the axial positions.
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Test your understanding of VSEPR theory with these flashcards. Each card provides key definitions and concepts related to valence-shell electron-pair repulsion theory and molecular shapes. Perfect for students studying chemistry!