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Electronegativity and Polarity. Electronegativity. The ability of an atom to attract electrons when bonded Nonmetals have high electronegativity Metals have low electronegativity Electronegativity increases across a period and decreases down a group. Nonpolar Covalent Bond.
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Electronegativity The ability of an atom to attract electrons when bonded • Nonmetals have high electronegativity • Metals have low electronegativity • Electronegativity increases across a period and decreases down a group
Nonpolar Covalent Bond • When electrons are shared between 2 atoms, a covalent bond is formed. • If the atoms are identical, e.g. Cl2, the electrons are shared equally (nonpolar)
Polar Covalent Bond • If the electrons are shared between 2 different atoms, e.g. HBr, the sharing is unequal • The bonding electrons spend more time near the more electronegative atom H Br
Electronegativity Differences • The absolute value of the difference in electronegativities of two bonded atoms provides a measure of polarity of a bond. • The greater the difference, the more polar the bond. 0 to 0.4 Nonpolar covalent 0.41 to 1.69 Polar covalent > 1.7 Ionic Electronegativity Difference
Polar Molecules • Note: Not all molecules with polar bonds are polar molecules