Abstract: In this paper, 3-2 IG ab initio calculations are performed on B₂H₆and its substituted derivatives of bridged atoms H₂B₂X₂(X=F, Cl, OH, NH₂, CH₃), these geometries are optimized with the energy gradient technique. According to the quantum chemical definition of atomic valence, the valences of bridged atoms are calculated to study the characteristics of bridged bond B-X-B, Some bridged boron hydrides B₄H₁₀, B₅H₉, and B₅H₁₁are also calculated to discuss the atomic valences and reactivities of bridged atoms.

Key words: Atomic valences, Boron Compouds, Bridged bond, Reactivities, Ab initio calculations