Podcast
Questions and Answers
Which shape corresponds to a molecule with two bonding pairs and a bond angle of 180 degrees?
Which shape corresponds to a molecule with two bonding pairs and a bond angle of 180 degrees?
Lone pairs exert less repulsion than bonding pairs.
Lone pairs exert less repulsion than bonding pairs.
False
What bond angle is associated with a tetrahedral shape?
What bond angle is associated with a tetrahedral shape?
109.5 degrees
In a molecule with four bonding pairs and no lone pairs, the shape is __________.
In a molecule with four bonding pairs and no lone pairs, the shape is __________.
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Match the following molecular shapes with their corresponding bond angles:
Match the following molecular shapes with their corresponding bond angles:
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What is the result of lone pairs on bond angles?
What is the result of lone pairs on bond angles?
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A molecule with five bonding pairs is likely to have a trigonal bipyramidal shape.
A molecule with five bonding pairs is likely to have a trigonal bipyramidal shape.
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Provide an example of a molecule with a nonlinear shape and how many bonding and lone pairs it has.
Provide an example of a molecule with a nonlinear shape and how many bonding and lone pairs it has.
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For a molecule with 3 bonding pairs and 1 lone pair, the bond angle is reduced to __________ degrees.
For a molecule with 3 bonding pairs and 1 lone pair, the bond angle is reduced to __________ degrees.
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What is the bond angle in an octahedral shape?
What is the bond angle in an octahedral shape?
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Study Notes
Molecular Shapes
- To determine molecular shapes, start with a simple dot-and-cross diagram.
- Identify the number of electron pairs (bonding and lone) around the central atom. Multiple bonds count as a pair of electrons.
- Count the number of bonding pairs and lone pairs.
- Analyze repulsion: Equal repulsion occurs when all electron pairs are bonding. Lone pairs repel more strongly than bonding pairs.
- Determine the associated shape and bond angle based on electron pair repulsion.
Shape Examples
- Two electron pairs (both bonding): Linear shape; 180° bond angle (e.g., CO2)
- Three electron pairs (all bonding): Trigonal planar shape; 120° bond angle (e.g., BF3)
- Three electron pairs (one lone pair): Bent shape; ≈ 117.5° bond angle (lone pairs reduce angle by ~2.5°).
- Four electron pairs (all bonding): Tetrahedral shape; 109.5° bond angle (e.g., CH4)
- Four electron pairs (one lone pair): Pyramidal shape; ≈ 107° bond angle (lone pair reduces angle).
- Four electron pairs (two lone pairs): Bent shape; ≈ 104.5° bond angle (lone pairs reduce angle).
- Five electron pairs (all bonding): Trigonal bipyramidal shape; 90°& 120° bond angles (e.g., PF5)
- Six electron pairs (all bonding): Octahedral shape; 90° bond angles (e.g., SF6)
General Guidelines
- Lone pairs reduce bond angles by approximately 2.5 degrees.
- The shape is determined primarily by the arrangement of bonding pairs.
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Description
This quiz explores the various molecular shapes based on electron pair repulsion theory. Participants will analyze dot-and-cross diagrams and identify bonding and lone pairs to determine molecular geometry. It includes examples such as linear, trigonal planar, and tetrahedral shapes.
