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How does electronegativity affect electron sharing in a covalent bond?
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covalent bond
In polar covalent bonds, such as that between hydrogen and oxygen atoms, the electrons are not transferred from one atom to the other as they are in an ionic bond. Instead, some outer electrons merely spend more time in the vicinity of the other atom. The effect of this orbital distortion is to induce regional net charges that hold the atoms together, such as in water molecules.
Electronegativity is defined as the ability of an atom to attract a shared pair of electrons toward itself when participating in a chemical bond. Its influence on electron sharing determines the nature and polarity of the bond:12
- Nonpolar Covalent Bonds: When two atoms have approximately equal electronegativities, they share the bonding electron pair equally. This results in an electrically uniform bond with little to no charge separation.123
- Polar Covalent Bonds: When atoms have different electronegativities, the more electronegative atom exerts a stronger pull on the shared electron pair. This causes the electrons to shift toward that atom, giving it a partial negative charge, while the other atom acquires a partial positive charge.243
- The Continuum to Ionic Bonding: As the difference in electronegativity between two atoms increases, the bond becomes increasingly polar. If the difference is very large, the more electronegative atom effectively gains complete control over the electron pair, and the bond is best characterized as ionic.243
Ultimately, covalent and ionic bonding represent a continuum rather than distinct categories, with the degree of electron sharing dictated by the relative electronegativities of the bonded atoms.24