Chemistry · Chemical Bonding · NEET
Higher bond order means SHORTER bond length. More shared electron pairs pull the two nuclei closer together. So a triple bond is shorter than a double bond, which is shorter than a single bond. Example: C≡C (triple) is shorter than C=C (double), which is shorter than C-C (single). This is a very common NEET comparison.
For a simple molecule, bond order = number of shared electron pairs between the two atoms. Single bond = 1, double bond = 2, triple bond = 3. For molecules like N2, O2, CO, CN- (studied with Molecular Orbital Theory), use bond order = (1/2)(bonding electrons - antibonding electrons). For NEET, memorize the common ones: N2 = 3, CO = 3, CN- = 3, O2 = 2, NO = 2.5, O2- = 1.5.
N2 has a triple bond (bond order 3) while O2 has a double bond (bond order 2). Higher bond order means the nuclei are held closer, so N2 has a shorter bond and needs more energy to break (higher bond enthalpy: N2 = 946 kJ/mol vs O2 = 498 kJ/mol). This exact trend N2 > O2 > H2 for bond enthalpy was tested in NEET 2025.
All three central atoms are sp3 hybridised, so the ideal angle is 109.5 degrees. But lone pairs push harder than bonded pairs (lone pair-bond pair repulsion is stronger). More lone pairs means a smaller angle. So the order is CH4 (109.5, zero lone pairs) > NH3 (107, one lone pair) > H2O (104.5, two lone pairs). NEET 2016 tested exactly this.
Yes, for bonds between the same or similar atoms. Higher bond order means more electron pairs holding the nuclei, so the bond is stronger (higher bond enthalpy) and shorter. So bond order is directly related to bond strength and inversely related to bond length. This one idea connects all three bond parameters.
Yes. Fractional bond order appears in species studied with Molecular Orbital Theory or in resonance. For example NO has bond order 2.5, O2- has 1.5, and O2+ has 2.5. In resonance structures like ozone (O3), each O-O bond has an average order of 1.5. A fractional value just means the real bond is between two whole-number types.
Which one of the following pairs of species have the same bond order?
Consider the species CN^+, CN^-, NO and CN. Which of these will have the highest bond order?
Identify the correct orders against the property mentioned: (A) H2O > NH3 > CHCl3 - dipole moment; (B) XeF4 > XeO3 > XeF2 - lone pairs on central atom; (C) O-H > C-H > N-O - bond length; (D) N2 > O2 > H2 - bond enthalpy. Choose the correct set.
Try the real previous-year questions from this chapter — each with the answer and a full solution.
Bond length is the distance between two bonded nuclei (measured in picometres). Bond angle is the angle between two bonds meeting at a central atom (in degrees). Bond order is the number of bonds between two atoms (a whole number or a fraction). They are linked: higher bond order gives shorter length and higher strength.
Memorize these: N2 = 3, CO = 3, CN^- = 3, NO^+ = 3, O2 = 2, NO = 2.5, O2^+ = 2.5, O2^- = 1.5, O2^2- = 1. Species with the same number of electrons (isoelectronic) usually have the same bond order.
More shared electron pairs between the two atoms increase the attraction between the electrons and the two nuclei, pulling the nuclei closer. So a triple bond is shorter than a double bond, which is shorter than a single bond.
Higher bond order means a stronger bond, so more energy is needed to break it. This is why bond enthalpy follows N2 > O2 > H2, matching their bond orders 3 > 2 > 1. NEET 2025 tested this exact trend.
Water (H2O) has two lone pairs on oxygen, while methane (CH4) has none. Lone pairs repel more strongly than bonded pairs, squeezing the bonds closer. So H2O is 104.5 degrees while CH4 is 109.5 degrees.
