Chapter 11: Problem 122
The distance between \(\mathrm{Li}^{+}\) and \(\mathrm{Cl}^{-}\) is \(257 \mathrm{pm}\) in solid \(\mathrm{LiCl}\) and \(203 \mathrm{pm}\) in an \(\mathrm{LiCl}\) unit in the gas phase. Explain the difference in the bond lengths.
Short Answer
Expert verified
The bond length is shorter in gas due to isolated ions lacking lattice interactions found in the solid state.
Step by step solution
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Bond Length
Bond length is the distance between the nuclei of two bonded atoms. In the context of ionic compounds like lithium chloride (
LiCl
), bond length refers to the distance between the positive ion (cation) and the negative ion (anion).
The bond length is influenced by several factors such as the size of the ions, the charge on the ions, and the environment in which they are present.
In a solid, these ions are part of an extended network, leading to a longer bond length compared to when the ions are in a gas phase, where they interact more directly due to the absence of a crystal lattice.
Hence, the LiCl bond length is greater in its solid form ( 257 pm ) than in its gaseous form ( 203 pm ).
This illustrates the impact of surrounding interactions and lattice effects on ionic bonds.
The bond length is influenced by several factors such as the size of the ions, the charge on the ions, and the environment in which they are present.
In a solid, these ions are part of an extended network, leading to a longer bond length compared to when the ions are in a gas phase, where they interact more directly due to the absence of a crystal lattice.
Hence, the LiCl bond length is greater in its solid form ( 257 pm ) than in its gaseous form ( 203 pm ).
This illustrates the impact of surrounding interactions and lattice effects on ionic bonds.
Solid Phase
The solid phase in chemistry refers to the state of matter characterized by a fixed shape and volume.
In the case of ionic compounds, like LiCl , the solid phase involves ions arranged in a repeating three-dimensional pattern known as a crystal lattice.
This structure leads to specific properties such as rigidity and high melting points.
In solid LiCl , each ion is influenced by the electrostatic forces from its neighbors in this lattice.
This interaction contributes to a longer bond length because each ion is surrounded by numerous opposite charges, which stabilize its position but also allow for more spatial allowance between ions.
Thus, the solid phase typically results in longer bond lengths compared to isolated molecules.
In the case of ionic compounds, like LiCl , the solid phase involves ions arranged in a repeating three-dimensional pattern known as a crystal lattice.
This structure leads to specific properties such as rigidity and high melting points.
In solid LiCl , each ion is influenced by the electrostatic forces from its neighbors in this lattice.
This interaction contributes to a longer bond length because each ion is surrounded by numerous opposite charges, which stabilize its position but also allow for more spatial allowance between ions.
Thus, the solid phase typically results in longer bond lengths compared to isolated molecules.
Gas Phase
The gas phase describes a state of matter where substances are easily compressible and assume the shape and volume of their container.
In the gas phase, ions like Li^+ and Cl^- in LiCl are no longer part of a crystal lattice, and they exist as separate entities.
This allows them to approach each other more closely, resulting in a shorter bond length.
The absence of lattice structure means that the ions are primarily influenced by their mutual attraction, leading to stronger and closer interactions.
The gas phase provides insights into the basic interactions between ions without the complicating influences of other surrounding ions, illustrating the concept of intrinsic bond strength and optimal bonding distance.
In the gas phase, ions like Li^+ and Cl^- in LiCl are no longer part of a crystal lattice, and they exist as separate entities.
This allows them to approach each other more closely, resulting in a shorter bond length.
The absence of lattice structure means that the ions are primarily influenced by their mutual attraction, leading to stronger and closer interactions.
The gas phase provides insights into the basic interactions between ions without the complicating influences of other surrounding ions, illustrating the concept of intrinsic bond strength and optimal bonding distance.
Crystal Lattice
A crystal lattice is an orderly, three-dimensional arrangement of atoms, ions, or molecules in a solid.
In ionic compounds like LiCl , this lattice plays a crucial role in determining physical properties like structure and stability.
The lattice is formed due to the electrostatic forces between oppositely charged ions that align in a repeating pattern.
This structure provides strength and rigidity to the compound but also influences the bond lengths within the lattice.
In the case of LiCl , the ions are further apart in the solid phase due to the necessity to fit into this rigid lattice pattern, leading to a longer bond length than in any isolated environment.
The significance of the crystal lattice is evident in the way it dictates structural arrangement and affects ionic interactions.
In ionic compounds like LiCl , this lattice plays a crucial role in determining physical properties like structure and stability.
The lattice is formed due to the electrostatic forces between oppositely charged ions that align in a repeating pattern.
This structure provides strength and rigidity to the compound but also influences the bond lengths within the lattice.
In the case of LiCl , the ions are further apart in the solid phase due to the necessity to fit into this rigid lattice pattern, leading to a longer bond length than in any isolated environment.
The significance of the crystal lattice is evident in the way it dictates structural arrangement and affects ionic interactions.
Electrostatic Forces
Electrostatic forces are the attractive or repulsive forces between charged particles. In ionic bonding, these forces are crucial as they are responsible for holding the ions together.
In the example of LiCl , Li^+ and Cl^- ions experience strong electrostatic forces that keep them bonded.
In the solid phase, these forces extend beyond individual ion pairs to a network of interactions within the crystal lattice.
This network results in a stabilizing effect but also leads to a longer bond distance because each ion must balance multiple interactions at once.
In the gas phase, without the influence of surrounding ions, the electrostatic attraction is more direct, resulting in a reduced bond length.
Understanding electrostatic forces allows for the comprehension of molecular integrity and bond strength in different phases.
In the example of LiCl , Li^+ and Cl^- ions experience strong electrostatic forces that keep them bonded.
In the solid phase, these forces extend beyond individual ion pairs to a network of interactions within the crystal lattice.
This network results in a stabilizing effect but also leads to a longer bond distance because each ion must balance multiple interactions at once.
In the gas phase, without the influence of surrounding ions, the electrostatic attraction is more direct, resulting in a reduced bond length.
Understanding electrostatic forces allows for the comprehension of molecular integrity and bond strength in different phases.
