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 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