Chemistry · Chemical Bonding · NEET
The difference is the number of shared electron pairs between the two atoms. A single bond shares 1 pair (2 electrons), shown as one line (A-B). A double bond shares 2 pairs (4 electrons), shown as two lines (A=B). A triple bond shares 3 pairs (6 electrons), shown as three lines (A#B). Example: H-H is single, O=O is double, N#N is triple.
Each shared pair has 2 electrons. So a single bond = 2 electrons shared, a double bond = 4 electrons shared, and a triple bond = 6 electrons shared. A common mistake is to say a double bond shares 2 electrons. It shares 2 pairs, which is 4 electrons.
A sigma (sigma) bond forms by head-on overlap of orbitals and is strong. A pi (pi) bond forms by sideways overlap and is weaker. A single bond is always 1 sigma bond. A double bond is 1 sigma + 1 pi. A triple bond is 1 sigma + 2 pi. So the first bond between two atoms is always sigma; extra bonds are pi. This is tested directly in NEET.
A triple bond is strongest, then double, then single. More shared electron pairs means more attraction pulling the two nuclei together, so more energy is needed to break it. Bond strength order: triple > double > single. For example N#N in nitrogen gas is very strong, which is why N2 is unreactive.
More shared electron pairs pull the two atoms closer, so the bond gets shorter. Bond length order: single > double > triple (triple is the shortest). For carbon-carbon: C-C is about 154 pm, C=C is about 134 pm, and C#C is about 120 pm. Shorter bond = stronger bond.
Rule: every single bond = 1 sigma. Every double bond = 1 sigma + 1 pi. Every triple bond = 1 sigma + 2 pi. Count every bond in the structure. Total sigma bonds = total number of bonds (single + double + triple all give 1 sigma each). Total pi bonds = (number of double bonds) + 2 x (number of triple bonds). This exact skill was asked in NEET 2019 and 2024.
Match List-I (Molecule) with List-II (Number and types of bond/s between the two carbon atoms). List-I: A. ethane; B. ethene; C. carbon molecule C2; D. ethyne. List-II: I. one sigma-bond and two pi-bonds; II. two pi-bonds; III. one sigma-bond; IV. one sigma-bond and one pi-bond.
The number of sigma (sigma) and pi (pi) bonds in pent-2-en-4-yne is:
Try the real previous-year questions from this chapter — each with the answer and a full solution.
In normal NEET chemistry the maximum is a triple bond (three shared pairs). Quadruple bonds exist only in some special metal compounds and are not part of the NEET syllabus.
No. A double bond has exactly 1 sigma bond and 1 pi bond. Between any two atoms there can be only one sigma bond; all extra bonds are pi bonds.
Bond length decreases as the number of shared pairs increases. Order: single > double > triple. The triple bond is the shortest and the single bond is the longest.
Yes. A pi bond is formed by weaker sideways overlap, so it is easier to break than a sigma bond. This is why double and triple bonds react at the pi bond in reactions like addition.
