Once you have the concept, the two atoms that share the bond can have no or little, medium, or large electronegativity difference, which is also called polarity. These “grading” corresponds to covalent, polar covalent and ionic bonds! Generally speaking, if the polarity is less than 0.4, it is called covalent. read more
If the electron density is much more withdrawn to the more electronegative atom an ionic bond is formed, if it less withdrawn by the more electronegative atom a polar covalent bond is formed, and equally distributed between two atoms a non-polar covalent bond is formed. read more
In nonpolar covalent bonds, electrons are shared equally by both members of the bond, but they are shared unequally in polar covalent bonds. Polar covalent bonds occur when there is a difference in electronegativity, or electron affinity, between covalently bonded atoms. read more
Polar covalent bonds are a particular type of covalent bond. In a polar covalent bond (for example water), the electrons shared by the atoms spend a greater amount of time, on the average, closer to the Oxygen nucleus than the Hydrogen nucleus. read more