Calculadora de Ordem de Ligação
- Created by
- Renato Passos, Eng. de Software
- Reviewed by
- Renato Passos, Eng. de Software
Last updated: Apr 18, 2026
Formula
OL = (eL − eA*) / 2
About this calculator
The Bond Order Calculator is a practical tool for chemistry students and professionals who want to quickly determine the stability and strength of a chemical bond using Molecular Orbital Theory. The bond order (BO) is calculated by the formula BO = (eB − eA*) / 2, where eB is the number of electrons in bonding orbitals and eA* is the number of electrons in antibonding orbitals. This value indicates how many effective bonds exist between two atoms: the higher the bond order, the stronger and more stable the bond.
Using it is simple: enter the number of bonding and antibonding electrons in the respective fields and click calculate. The result appears immediately, as an integer, decimal, or fraction. For example, in the N₂ molecule, with 10 bonding electrons and 4 antibonding electrons, the bond order is (10 - 4)/2 = 3, indicating a strong triple bond. In H₂, with 2 bonding electrons and 0 antibonding electrons, the BO is 1, representing a single bond.
Use this calculator in academic contexts, such as solving quantum chemistry exercises, or in research involving diatomic molecule analysis. It is useful for comparing the stability of different species, predicting bond lengths, and understanding magnetic properties (molecules with unpaired electrons in antibonding orbitals are paramagnetic). Remember that the formula mainly applies to homonuclear and simple heteronuclear diatomic molecules.
Cautions: theoretical bond order does not always match experimental values due to electron correlation effects and hybridization. Ensure correct counting of electrons in molecular orbitals, especially for ions or charged molecules. For polyatomic molecules, bond order is an average between atom pairs, and this calculator is best suited for diatomic systems.
Frequently asked questions
What does a bond order of zero mean?
It indicates no effective bond between the atoms, as the number of bonding electrons equals antibonding electrons. Molecules with zero bond order are unstable and usually do not exist under normal conditions.
Can I use this calculator for polyatomic molecules?
It is designed for diatomic molecules. For polyatomic, bond order is calculated for each atom pair individually, and the average may be used, but the result may not accurately reflect the actual bond.
How do I count bonding and antibonding electrons?
Refer to the molecular orbital diagram of the molecule. Electrons in lower energy orbitals (sigma, pi bonding) are bonding; those in higher energy orbitals (sigma*, pi* antibonding) are antibonding. Sum the electrons in each type.
Can bond order be a fractional number?
Yes, it is common in molecules with unpaired electrons or ions. For example, the O₂⁻ ion has a bond order of 1.5, indicating a bond between single and double.
What is the difference between bond order and bond length?
Bond order is a theoretical measure of bond strength; bond length is the experimental distance between nuclei. Generally, higher bond order corresponds to shorter bond length.