Hybridization of an atom can be determined directly by counting the number of atoms sigma-bonded to it plus its number of lone pairs, since that sum equals the number of hybrid orbitals required (two → sp, three → sp², four → sp³), with the exception that single-bonded terminal atoms (and hydrogen) remain unhybridized; sigma bonds form from hybrid orbitals oriented along the internuclear axis while pi bonds form from unhybridized, parallel p orbitals. Separately, bond enthalpy (the heat associated with breaking a bond, closely related to but distinct from bond dissociation energy) can be tabulated as mean/average values for a given bond type and used to calculate the enthalpy of an entire reaction as the difference between bonds broken (reactants) and bonds formed (products), or equivalently via tabulated heats of formation, since enthalpy is a path-independent state function. This belongs to physical/general chemistry, spanning valence bond theory (structure and bonding) and thermochemistry (energetics of reactions).
Hybridization of an atom can be determined directly by counting the number of atoms sigma-bonded to it plus its number of lone pairs, since that sum equals the number of hybrid orbitals required (two…