In the Basic tab, enter the covalent radii of two atoms and the electronegativity of each atom to estimate the bond length.
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Bond Length Formula
The following empirical formula (Schomaker–Stevenson style) can be used to estimate a covalent bond length when the radii are in ångströms (Å).
d_{A-B}=r_A+r_B-0.09\left|\chi_A-\chi_B\right|- Where dA-B is the distance between the nuclei of atoms A and B
- rA is the covalent radius of atom A
- rB is the covalent radius of atom B
- χA is the electronegativity of atom A
- χB is the electronegativity of atom B
Bond Length Definition
What is a bond length? A bond length is a measure of the distance between the centers of two bonded nuclei. The distance is typically reported in picometers (pm) or ångströms (Å).
Example
How to calculate bond length?
- First, determine the lengths of the covalent radii.
For this example, the radius of atom A is 24 picometers and the radius of atom B is 32 picometers.
- Next, determine the electronegativity of atom A.
For this problem, atom A has an electronegativity of 3.2.
- Next, determine the electronegativity of atom B.
The electronegativity of atom B is found to be 2.1.
- Finally, calculate the bond length.
Convert radii to Å: 24 pm = 0.24 Å and 32 pm = 0.32 Å. Then dA-B = 0.24 + 0.32 − 0.09·|3.2 − 2.1| = 0.461 Å (46.1 pm).
About Bond Length
Is bond length an average? In general, measured bond lengths are averages over molecular motion (vibration/rotation), while an equilibrium bond length refers to the internuclear distance at the minimum of the potential energy curve.
How does bond length change with bond order? As bond order increases, the bond length will decrease. For example, a bond order of three (a triple bond) will have a smaller bond length than a bond order of two (a double bond).
