Comparing Ionic Bonds and Covalent Bonds
Recall : Ionic bonds  ______________ + __________________
Recall : Covalent bonds  ________________ + ____________________
Besides the types of atoms that form the bonds, ELECTRONEGATIVITY (En) of an element will also
determine the type of chemical bond that forms.
Electronegativity (En) is a measure of the relative ability of an element’s atoms to attract electrons when
forming any type of chemical bond. Each element has its own Envalue (no units) shown on the Table of
Electronegativities.
The type of chemical bond that occurs can be predicted by finding the difference in electronegativity
(∆En) between the two atoms forming the chemical bond.



If the ∆En > 1.7, then the chemical bond is likely an IONIC BOND;
If the ∆En < 1.7, then the chemical bond is likely a COVALENT BOND.
There are two types of covalent bonds :
- Polar Covalent Bond : if the ∆En is greater than 0.5 but less than 1.7;
- Nonpolar Covalent Bond : if the ∆En is less than 0.5.
Ex.1 Do the following pairs of atoms form ionic bonds or covalent bonds?
a) phosphorus and chlorine - ____________________ ∆En = _________
b) aluminum and fluorine - ___________________
∆En = ________
Ex.2 Are the following covalent bonds polar or nonpolar?
a) H—Cl : ________________ ∆En = _________
b) C—H : ________________ ∆En = _________
c) O=O : _________________ ∆En = _________
Polar and Nonpolar Molecular Compounds
A molecular compound is POLAR if :
1) It has polar covalent bonds AND;
2) It has unbalanced forces, caused by such things as lone pairs of electrons on the “central atom” of
the molecule or an odd assortment of atoms bonded to the “central atom”.
3) A molecular compound is NONPOLAR if it has nonpolar covalent bonds and balanced forces.
Intermolecular Forces : the forces of attraction that happen BETWEEN molecules, whether ionic or
molecular.
Ionic compounds have very strong dipole-dipole force attractions.
Polar covalent compounds have strong dipole-dipole force attractions. Nonpolar covalent compounds
have weaker intermolecular forces called London Dispersion forces.