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The bond order itself is the number of electron pairs (covalent bonds) between two atoms. [3] For example, in diatomic nitrogen N≡N, the bond order between the two nitrogen atoms is 3 (triple bond). In acetylene H–C≡C–H, the bond order between the two carbon atoms is also 3, and the C–H bond order is 1 (single bond).
The drawback of this approach is that the equations may become unwieldy and complex; for example, the mass matrix M may become non-diagonal and depend on the generalized coordinates. A second approach is to introduce explicit forces that work to maintain the constraint; for example, one could introduce strong spring forces that enforce the ...
Structural and chemical properties, such as bond order, valency, and bond polarity, may be calculated from resonance weights. [2] Specifically, bond orders may be divided into their covalent and ionic contributions, while valency is the sum of bond orders of a given atom.
This is more than the naive π-bond order of (for a total bond order of ) that one might guess when simply considering the Kekulé structures and the usual definition of bond order in valence bond theory. The Hückel definition of bond order attempts to quantify any additional stabilization that the system enjoys resulting from delocalization.
The reactive empirical bond-order (REBO) model is a function for calculating the potential energy of covalent bonds and the interatomic force.In this model, the total potential energy of system is a sum of nearest-neighbour pair interactions which depend not only on the distance between atoms but also on their local atomic environment.
Valence bond theory; Coulson–Fischer theory Generalized valence bond Modern valence bond theory: Molecular orbital theory; Hartree–Fock method Semi-empirical quantum chemistry methods Møller–Plesset perturbation theory Configuration interaction Coupled cluster Multi-configurational self-consistent field Quantum chemistry composite methods
A bond of higher bond order also exerts greater repulsion since the pi bond electrons contribute. [10] For example in isobutylene, (H 3 C) 2 C=CH 2, the H 3 C−C=C angle (124°) is larger than the H 3 C−C−CH 3 angle (111.5°). However, in the carbonate ion, CO 2− 3, all three C−O bonds are equivalent with angles of 120° due to resonance.
Wavy single bonds represent unknown or unspecified stereochemistry or a mixture of isomers. For example, the adjacent diagram shows the fructose molecule with a wavy bond to the HOCH 2 - group at the left. In this case the two possible ring structures are in chemical equilibrium with each other and also with the open-chain structure.