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Questions and Answers
What is the correct unit of measurement for bond length?
What is the correct unit of measurement for bond length?
Which physical method is commonly used to measure bond lengths?
Which physical method is commonly used to measure bond lengths?
What happens to the bond length as the number of bonds between two atoms increases?
What happens to the bond length as the number of bonds between two atoms increases?
How does the percentage of s-character affect bond length?
How does the percentage of s-character affect bond length?
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Which of the following statements correctly describes the effect of atomic size on bond length?
Which of the following statements correctly describes the effect of atomic size on bond length?
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In terms of covalent radius, how is bond length determined?
In terms of covalent radius, how is bond length determined?
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Which bond length is expected to be the shortest?
Which bond length is expected to be the shortest?
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Which of the following indicates a stronger effect on bond length?
Which of the following indicates a stronger effect on bond length?
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Study Notes
Bond Length Definition
- The average distance between the nuclei of two bonded atoms.
- Units of measurement: picometer (pm), angstrom (Å), and nanometer (nm).
Bond Length Examples
- Cl-Cl bond length: 198 pm
- C-C single bond length: 154 pm
Measurement of Bond Length
- Physical method: X-ray Diffraction Method
- This method involves measuring the diffraction angle of X-rays when they pass through a substance (ionic or covalent).
- The bond length can be calculated using Bragg's equation.
Factors Affecting Bond Length
- Connectivity: The type of atoms involved in the bond.
- Electronegativity difference: The difference in electronegativity between the two atoms.
- Number of bonds between two atoms: Single, double, and triple bonds.
- Percentage of s-character: The proportion of s-orbital character in the hybrid orbital involved in bonding.
Relationship Between Bond Length and Covalent Radius
- Additive Property: The bond length is roughly equal to the sum of the covalent radii of the two bonded atoms.
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Examples:
- Cl-Cl bond length: 99 pm + 99 pm ≈ 198 pm
- C-Cl bond length: 77 pm + 99 pm ≈ 176 pm
Effect of Number of Bonds
- Increase in the number of bonds between two atoms leads to a decrease in bond length.
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Example:
- C-C single bond (154 pm) > C=C double bond (134 pm) > C≡C triple bond (120 pm)
Effect of Percentage of s-character
- Increased s-character leads to a shorter bond length.
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Example:
- sp3 hybridization (33% s-character): Longer bond
- sp2 hybridization (50% s-character): Shorter bond
- sp hybridization (66% s-character): Shortest bond
Effect of Atomic Size
- As atomic size increases, bond length increases.
- Down a group in the periodic table: Atomic size increases, leading to longer bonds.
- Example: Na-Cl bond length > K-Cl bond length
- Across a period in the periodic table: Atomic size decreases, leading to shorter bonds.
- Example: C-Cl bond length < N-Cl bond length
Summary of Important Points
- Factors affecting bond length: Connectivity, electronegativity difference, number of bonds, percentage of s-character, and atomic size.
- Relationship between bond length and covalent radius: Additive property.
- Effect of increasing number of bonds: Decreases bond length.
- Effect of increasing s-character: Decreases bond length.
- Effect of increasing atomic size: Increases bond length.
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Description
Explore the concept of bond length in chemistry, including its definition, measurement methods, and factors affecting it. Understand how bond length relates to the types of atoms and bonding interactions within molecules.
