Electronegativity determines the distribution of shared electrons in a covalent bond. The higher the electronegativity of an atom in a covalent bond, the more strongly it attracts the shared electrons towards itself.
Here's a more detailed breakdown:
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Equal Electronegativity: When two atoms with similar electronegativities form a covalent bond, the electrons are shared relatively equally. This results in a nonpolar covalent bond. An example of this is the bond between two hydrogen atoms (H2).
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Unequal Electronegativity: When two atoms with significantly different electronegativities form a covalent bond, the electrons are shared unequally. The more electronegative atom attracts the electrons more strongly, resulting in a polar covalent bond.
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Partial Charges: In a polar covalent bond, the more electronegative atom gains a partial negative charge (δ-), while the less electronegative atom gains a partial positive charge (δ+).
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Dipole Moment: This separation of charge creates a dipole moment in the bond, indicating the polarity of the bond.
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Example:
Consider the bond between hydrogen (H) and chlorine (Cl) in hydrogen chloride (HCl). Chlorine has a higher electronegativity than hydrogen. Therefore, chlorine attracts the shared electrons more strongly, resulting in:
- A partial negative charge (δ-) on the chlorine atom.
- A partial positive charge (δ+) on the hydrogen atom.
- A polar covalent bond with a dipole moment pointing towards the chlorine atom.
Summary Table:
| Electronegativity Difference | Bond Type | Electron Distribution |
|---|---|---|
| Small (0 - 0.4) | Nonpolar Covalent | Evenly shared |
| Intermediate (0.4 - 1.7) | Polar Covalent | Unevenly shared |
| Large (Greater than 1.7) | Ionic | Transferred |
In essence, electronegativity differences between atoms forming a covalent bond dictate whether the bond is nonpolar (equal sharing) or polar (unequal sharing), and the extent of polarity is directly related to the electronegativity difference.
