The Hydrogen Fluoride Molecule

This is a representation of the electron cloud about the hydrogen and fluorine atoms. The electron clouds about each atom in this molecule are not identical. The electrons are not shared equally between the two nuclei because H and F do not attract electrons equally.

The unsymmetrical distribution of the electron cloud shows that the electron cloud is distorted in the direction of the more electronegative F atom. This observed shift of electron cloud leaves the H end of the molecule slightly positive when compared to the F end. This is a polar covalent bond

To represent an imbalanced of electron cloud, the by the H end of the molecule indicates a slight positive charge with respect to the F end.

The by the F end of the molecule indicates a slight negative charge with respect to the H end.

Another way to indicate the polarity of the bond is to draw the bond dipole moment. The is represented by an arrow that points toward the negative end of the bond. A "+" is placed at the tail of the arrow to indicate the positive end of the bond.

Other molecules with polar covalent bonding are:

These also have polar covalent bonding because the atoms involve in the bonding have different electronegativities.