Bond Energy
The energy required to break one mole of a given bond homolytically in the gaseous state.
Formula / equation
A–B(g) → A(g) + B(g)
Unit
kJ/mol
In depth
Tabulated values are averages over many compounds, since the exact strength depends on the surrounding structure. Bond energies allow reaction enthalpies to be estimated as bonds broken minus bonds formed, and they explain why some molecules are kinetically inert despite being thermodynamically unstable.
Examples in the real world
H–H is 436 kJ/mol, C–H 413 kJ/mol, and N≡N 945 kJ/mol — the reason nitrogen fixation is so demanding.