A single bond is a covalent bond in which two atoms share one pair of electrons (bond order = 1). On the AP Chem exam, it matters because single bonds are longer and weaker than double or triple bonds between the same atoms, which shows up in potential energy graphs and bond enthalpy calculations.
A single bond is the simplest covalent bond. Two atoms share exactly one pair of electrons, which gives the bond a bond order of 1. In a Lewis structure, you draw it as one line between atoms, like the C-C bond in ethane or every P-P bond in white phosphorus.
The AP-relevant part is what bond order does to the bond's properties. Per the CED (2.2.A.2), bonds with higher order are shorter and have larger bond energies. So a C-C single bond is the longest and weakest of the carbon-carbon family. The numbers back this up. Breaking C-C takes about 348 kJ/mol, C=C takes 614 kJ/mol, and CโกC takes 839 kJ/mol. Think of it like rope. One strand of shared electrons holds the atoms together, but two or three strands pull them closer and hold them tighter. That single-strand bond is also the easiest to break, which is exactly why single-bond energies show up in enthalpy estimates in Unit 6.
Single bonds live in two places in the CED. In Topic 2.2 (Unit 2), learning objective 2.2.A asks you to interpret potential energy versus internuclear distance graphs. The bottom of the curve marks the equilibrium bond length, and the depth of the well marks the bond energy. A single bond produces a shallower, wider well than a double or triple bond between the same atoms (longer bond, less energy to break). In Topic 6.7 (Unit 6), learning objective 6.7.A has you calculate reaction enthalpy from average bond energies. You add up the energy needed to break the bonds in the reactants, subtract the energy released forming bonds in the products, and the sign tells you exothermic or endothermic. Knowing that single bonds are the weakest bond type lets you predict and explain those energy changes, not just plug numbers.
Keep studying AP Chemistry Unit 2
Triple Bond (Unit 2)
Same atoms, three shared pairs instead of one. A triple bond is shorter and much stronger, so on a potential energy graph its well sits deeper and closer to the y-axis than a single bond's well. Compare 348 kJ/mol for C-C to 839 kJ/mol for CโกC.
Potential Energy and Internuclear Distance (Unit 2)
Every covalent bond, single bonds included, is really a balance of Coulombic attractions and repulsions. The single bond's equilibrium bond length is just the internuclear distance where potential energy bottoms out. Bond order shifts where that bottom sits.
Bond Enthalpy Calculations (Unit 6)
When you estimate ฮH from average bond energies, you have to correctly count single versus double bonds in your Lewis structures first. Misreading a C=C as a C-C throws your answer off by hundreds of kJ/mol.
Coulomb's Law (Units 1-2)
Bond strength comes down to charge and distance. More shared electron pairs means more negative charge concentrated between the nuclei, which pulls the atoms closer and deepens the attraction. That's why one pair (a single bond) gives the weakest covalent pull.
Multiple-choice questions love the bond order pattern. You'll see stems giving bond dissociation energies for C-C, C=C, and CโกC and asking which statement about length or strength is accurate, or asking you to rank which bond is shortest. The rule to apply is higher bond order means shorter bond and larger bond energy. On the free-response side, the 2025 LRFRQ Q3 described white phosphorus (Pโ), where each P atom forms single bonds to three others, and asked you to work with that structure. FRQs also commonly hand you average bond energies and have you calculate ฮH for a reaction (like Hโ + Oโ โ HโO releasing 572 kJ), then explain whether it's exothermic or endothermic in terms of bonds broken versus bonds formed. The skill isn't memorizing what a single bond is. It's using bond order to justify trends in length, energy, and enthalpy.
All three are covalent bonds; they differ only in how many electron pairs are shared. A single bond shares one pair, a double shares two, a triple shares three. The trade-off the exam tests: as bond order goes up, bond length goes down and bond energy goes up. So a single bond is the longest and weakest of the set, never the strongest. If a question says 'shortest bond,' look for the highest bond order, not the single bond.
A single bond is a covalent bond where two atoms share one pair of electrons, giving a bond order of 1.
Single bonds are longer and weaker than double or triple bonds between the same atoms, because higher bond order pulls atoms closer with more bond energy (CED 2.2.A.2).
On a potential energy versus internuclear distance graph, a single bond has a shallower energy well and a longer equilibrium bond length than a multiple bond.
In bond enthalpy problems (Topic 6.7), breaking single bonds costs energy and forming them releases energy, and the difference determines whether the reaction is exothermic or endothermic.
Real data makes the trend concrete: C-C is 348 kJ/mol, C=C is 614 kJ/mol, and CโกC is 839 kJ/mol.
A single bond is a covalent bond where two atoms share one pair of electrons (bond order of 1), drawn as one line in a Lewis structure. It's the longest and weakest type of covalent bond between a given pair of atoms.
No. Single bonds are weaker and longer than double bonds between the same atoms. For example, breaking a C-C single bond takes 348 kJ/mol while a C=C double bond takes 614 kJ/mol.
A single bond is covalent, meaning the two atoms share an electron pair. An ionic bond involves a full transfer of electrons, creating oppositely charged ions held together by Coulombic attraction. Single bonds form between nonmetals; ionic bonds typically form between metals and nonmetals.
More shared electron pairs concentrate more negative charge between the two nuclei, pulling the atoms closer together. With only one shared pair, a single bond has the weakest attraction and so the atoms sit farther apart, per CED 2.2.A.2.
No, breaking any bond always requires energy. Energy is released when bonds form. A reaction is exothermic when the energy released forming product bonds exceeds the energy needed to break reactant bonds, like Hโ reacting with Oโ to form water and releasing 572 kJ.