A single bond, or single covalent bond, is a type of chemical bond wherein a pair of electron is shared between two atoms bonding with each other. In other words, a couple of electrons will be shared during the process – one electron each from both atoms. As the electrons are shared and not transferred, these bonds come under the covalent bond category.
Post-sharing, the electrons become part of both atoms or hover within the orbit of both atoms. For example, the water molecule is a single bond, wherein both the hydrogen and oxygen atoms share an electron each and merge, as a result. On a Lewis structure diagram, single bonds are represented by a single horizontal line or dash linking the bonded atoms.
Strength and Length
The more the number of electrons involved in a bond, the stronger the bond and the shorter its length because the higher attraction force and increased bonding overlap bring the atoms even closer. Since a single bond entails two electrons, it’s not as strong as double and triple bonds and the length is longer too. Also, a single bond comprises only a sigma bond. There are no pi bonds unlike a double and triple bond. A sigma bond is an atom’s orbital overlapping the other atom’s orbital head-to-head.