Textbook Question
(a) Rank the following bonds in terms of the strength of their bond dipole (1 = weakest, 6 = strongest).
(b) Which carbon has the largest δ⁺ ?
C―F, C―Br, C―I, C―H, C―C, C―Cl
1. A Review of General Chemistry
Electronegativity
Problem 11e,f
Textbook Question
Use the symbols δ+ and δ− to show the direction of the polarity of the indicated bond in each of the following compounds:
e. HO—Br
f. H3C—Li
Verified step by step guidance1
Step 1: Understand the concept of bond polarity. Bond polarity arises due to the difference in electronegativity between two atoms in a bond. The atom with higher electronegativity attracts the shared electrons more strongly, acquiring a partial negative charge (δ−), while the less electronegative atom acquires a partial positive charge (δ+).
Step 2: Analyze the electronegativity of the atoms in the HO—Br bond. Oxygen (O) has a higher electronegativity compared to bromine (Br). Therefore, the shared electrons in the bond will be closer to the oxygen atom, making oxygen δ− and bromine δ+.
Step 3: Represent the polarity of the HO—Br bond using δ+ and δ− symbols. Place δ− on the oxygen atom and δ+ on the bromine atom to indicate the direction of electron density shift.
Step 4: Analyze the electronegativity of the atoms in the H3C—Li bond. Carbon (C) is more electronegative than lithium (Li). As a result, the shared electrons in the bond will be closer to the carbon atom, making carbon δ− and lithium δ+.
Step 5: Represent the polarity of the H3C—Li bond using δ+ and δ− symbols. Place δ− on the carbon atom and δ+ on the lithium atom to indicate the direction of electron density shift.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Polarity of Bonds
Polarity in chemical bonds arises from the difference in electronegativity between the atoms involved. When two atoms form a bond, the atom with higher electronegativity attracts the shared electrons more strongly, resulting in a partial negative charge (δ−) on that atom and a partial positive charge (δ+) on the other. This creates a dipole moment, indicating the direction of electron density and the bond's polarity.
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Electronegativity
Electronegativity is a measure of an atom's ability to attract and hold onto electrons in a chemical bond. It varies across the periodic table, with elements like fluorine being highly electronegative. Understanding the relative electronegativities of the atoms in a bond helps predict the bond's polarity, as greater differences lead to more polar bonds.
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Dipole Moment
A dipole moment is a vector quantity that represents the separation of positive and negative charges in a molecule. It is calculated as the product of the charge and the distance between the charges. In the context of polar bonds, the dipole moment points from the positive end (δ+) to the negative end (δ−), indicating the direction of the bond's polarity and influencing the molecule's overall behavior in electric fields.
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