Electronegativity+and+polarity

Electro negativety
 * Although covalent molecules are uncharged overall,the electron density surrounding each atom may be different.
 * If an atom has a greater tendency to draw/attract electrons,this is a highly electronegative atom. EG: Nitrogen,Oxygen,Fluorine.
 * The more electro negative atom will result in a delta minus at it,and the less electro negative atom will result in a delta plus at it.Resulting in a dipole moment,creating a polar bond.
 * The smaller the atom,the greater the tendency to attract electrons.
 * The higher the effective nuclear charge,greater tendency to attract electrons.
 * [[image:http://rpmedia.ask.com/ts?u=/wikipedia/en/d/d9/Polarity_boron_trifluoride.png]][]

Polarity


 * A molecule with polar bonds may not be a polar molecule because the dipole moments may cancel each other.
 * Molecules like Cl2 are not polar,but they have temporary dipole-dipole.
 * Molecules with double covalent bonds that are linear like carbon dioxide are non-polar.