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Molecular-Orbital Electron Counts & Bond Order

Find molecular-orbital bond order from bonding and antibonding electron counts, including zero net bond order.

  • Formula & worked example
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Calculator inputs

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How to use this calculator

  1. Enter the known values in the units shown. Results update as you type.
  2. Where results are editable, change one to solve backwards. Lock a value to hold it fixed.
  3. Use the worked example to check the method. Reset restores the starting fields.

Private by default

Inputs and results stay in this browser tab. Bookify does not upload or store the values you enter.

Formula and method

Eight bonding electrons and four antibonding electrons give bond order 2. Equal counts of two and two give bond order 0.

Bond order = (bonding electrons − antibonding electrons) / 2

Worked example

Enter these known values and leave the other values blank.

Electrons in bonding orbitals
8
Electrons in antibonding orbitals
4
Net molecular-orbital bond order
2

Assumptions and limitations

  • Electron populations are nonnegative whole numbers; this tool supports bonding population at least as large as antibonding population.
  • Zero means no net bonding contribution in this elementary orbital-count model. A positive number does not by itself establish the stability or structure of a real molecule.
  • Half-integer results are possible for odd differences in electron population. Use a consistent molecular-orbital configuration; do not mix a valence-only count on one side with an all-electron count on the other.

Common questions

Can a valid result be zero?

Yes. Equal bonding and antibonding populations cancel in this model, as in the elementary molecular-orbital treatment of hypothetical dihelium.

Can bond order be fractional?

An odd difference in whole electron populations gives a half-integer result, such as 0.5 or 1.5.

References

Bookify permits zero bond order with equal bonding and antibonding populations, while requiring nonnegative whole electron counts and nonnegative half-integer bond order.

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