L7.3.1: Electronegativity and Polarity

• A covalent bond in which the shared electron pair is not shared equally, but remains closer to one atom than the other, is a polar covalent bond.
• The ability of an atom in a covalent bond to attract the shared electron pair is called its electronegativity.
• Unequal sharing of electrons causes the more electronegative atom of the bond to be partially negative and the less electronegative atom to be partially positive.
• The most electronegative element is fluorine.
• In general electronegativity decreases down a group as atomic size increases.

  In general electronegativity increases across a period as atomic size decreases.
• Nonmetals are more electronegative than metals.
• The unequal sharing of electrons can be depicted by a polar arrow. The head of the arrow points to the more electronegative element.
• A polar bond can also be marked using δ+ and δ- symbols.