Breathing orbital valence bond (BOVB) computations (Hiberty, P. C.; Humbel, S.; Archirel, P. J. Phys. Chem. 1994, 98, 11697) are used to obtain identity barriers for hydrogen transfer reactions between X groups, X = H, CH3, SiH3, GeH3, SnH3, and PbH3. Modeling of these barriers by means of VB state correlation diagrams (Shaik, S.; Shurki, A. Angew. Chem. 1999, 38, 586) lead to simple expressions for the barriers (eqs 21 and 22). These expressions show that the organizing quantity of the barriers is the singlet-triplet excitation energy (DeltaE(ST)) or bond energy (D) of the X-H bond that undergoes activation. The larger the DeltaE(ST) or D, the higher the identity barrier. These equations are successfully applied to deduce barriers for hydrogen transfers between electronegative groups, X = X' = F, Cl, Br, and I. The "polar effect" (Russell, G. A. In Free Radicals; Kochi, J. K., Ed.; Wiley: New York, 1973; Vol 1, p 293-298) is shown to be significant but virtually constant in the series. Thus, identity processes mask the polar effect which is more clearly expressed in nonidentity hydrogen transfer reactions. Generalization of the model to other atom transfer reactions is discussed.