Steric Factor
The fraction of sufficiently energetic collisions that also have the correct spatial orientation for reaction.
Formula / equation
p = A / Z
Unit
Dimensionless
In depth
The steric factor is always less than one and can be as small as 10⁻⁶ for reactions of large, complex molecules that must meet at a specific site. Simple atomic reactions have values close to one, since almost any approach geometry works.
Examples in the real world
Enzyme–substrate reactions have very low steric factors, which is precisely why enzymes must orient their substrates.