Does Bond Length Always Equal Bond Strength?

[Dr. Nick]

Bond length, Bond strength, relationship ?

Is this always true ? And why? My answer to this question would be, having larger electron density between two nuclei, thus attraction, allows them to position more closely.

But somehow I think that there could be some exceptions of this rule, maybe in molecules of heavy atoms with many subvalece orbital not allowing them to be at close range, but still having strong bonds with good overlap.

Or, if this rule is absolutely and always true, I would say that bond strength decrease as atomic number increases (throughout period system), and molecules of atoms with larger number of orbital and electrons are less stabile.


edit:i've fixed the title
... :) well I've tried

 

[movies]

No, this is not always the case. Take for example F₂ and Cl₂; the bond lengths are 142 and 199 pm, respectively. The bond energies, however, are 158 and 243 kJ, respectively.

Another example (where one atom is kept constant) would be a C-N and a C-Cl bond. The C-N bond is 147 pm, the C-Cl, 177 pm. The energies are 308 and 330 kJ, respectively.

Data are from http://www.science.uwaterloo.ca/~cchieh/cact/c120/bondel.html

 

[Gokul43201]

For anyone that is confused by the title, I'm quite sure the OP is talking about the usual inverse relationship between bond-length and bond strength.