Chapter 5: Problem 20

Why does the presence of a lone pair change the shape of the molecule?

Short Answer

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Answer: The presence of a lone pair on the central atom changes the shape of the molecule because these lone pair electrons take up more space due to their negative charge and push the atoms further away. This causes a distortion in the molecular geometry, making it different from the electron pair geometry. The change in molecular shape has a direct impact on the molecule's properties and behavior, such as reactivity, polarity, and intermolecular interactions.

Step by step solution

Understanding electron pair geometry and molecular geometry

Electron pair geometry refers to the arrangement of electron pairs (bonding and lone pairs) around the central atom in a molecule. Molecular geometry, on the other hand, refers to the arrangement of only the atoms in a molecule.

The role of lone pairs in electron pair geometry

Lone pairs are valence electrons that are not shared between atoms, while bonding pairs are valence electrons that are shared between two atoms. In a molecule, both lone pairs and bonding pairs occupy space around the central atom and repel each other due to the negatively charged nature of electrons. This repulsion determines the overall spatial arrangement of electron pairs, which in turn determines the shape of the molecule.

Effect of lone pairs on molecular shape

The presence of a lone pair on the central atom changes the shape of the molecule because these lone pair electrons take up more space due to their negative charge and push the atoms further away. This causes a distortion in the molecular geometry, making it different from the electron pair geometry. For example, a molecule with trigonal planar electron pair geometry and one lone pair (such as ammonia, NH3) will have a bent (or V-shaped) molecular geometry.

Importance of molecular shape

The shape of a molecule plays a crucial role in its properties, such as reactivity, polarity, and intermolecular interactions. If the presence of a lone pair alters the shape of the molecule, this can significantly affect these properties. In conclusion, the presence of a lone pair changes the shape of a molecule because lone pairs occupy space around the central atom, causing a distortion in the molecular geometry. This change in molecular shape has a direct impact on the molecule's properties and behavior.

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Why does the presence of a lone pair change the shape of the molecule?

Short Answer

Step by step solution

Understanding electron pair geometry and molecular geometry

The role of lone pairs in electron pair geometry

Effect of lone pairs on molecular shape

Importance of molecular shape

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