Shared pairs of electrons
A single covalent bond contains a shared pair of electrons. Covalent bonds normally form between non-metal atoms, with electrons shared rather than transferred from one atom to another.
The negatively charged shared pair is attracted to the positively charged nuclei of both bonded atoms. This electrostatic attraction holds the atoms together.
Sharing electrons often allows each bonded atom to obtain a complete outer shell, similar to a noble-gas electron arrangement.
- Each atom contributes electrons to the bonding region.
- The bonding electrons are shared between both atoms.
- One shared pair forms one covalent bond.
- A covalent bond can be represented by a line between the bonded atoms.
The shared pair lies between the two bonded atoms.
Hydrogen, chlorine, hydrogen chloride, ammonia, methane and ethane are examples in which atoms are joined using single covalent bonds.
Exam Tip: If asked what a single covalent bond contains, state a shared pair of electrons. Do not describe covalent bonding as electron transfer.