bond strength

[li5504552]

-I am confused why in GS textbook it says that non-polar bonds are stronger than polar covalent bonds which are stronger than ionic. I thought that polar covalent bonds were stronger than non-polar bonds? Aren't ionic bonds stronger than covalent bonds? Thanks.

[admin]

A non-polar bond (ie like the diatomic molecule Cl2) is perfectly equally shared so it is very strong. A polar covalent bond (also called a covalent bond with ionic character, like HF or HCl) is weaker because one of the atoms pulls on the electrons in the bond more that the other atom. It increases the likelihood of the bond breaking since one of the atoms wants to tear away the electrons in the bond.

Now regarding the difference of strength of ionic vs covalent bonds, it is not a matter that would be asked on the MCAT only because the number of exceptions makes the rule shaky (this was alluded to in the book due comparing a bond with the entire compound). The MCAT would compare strong bonds like ionic and covalent with weak bonds like H-bonds, Van der Waal's and dipole-dipole electrostatic intermolecular bonds.