HH
Single bond
One pair of electrons is shared. Example: hydrogen gas, H2.
Overview
What is a covalent bond?
A covalent bond is a chemical bond where two atoms share one or more pairs of electrons. The shared electrons spend time near both nuclei, pulling the atoms together.
Covalent bonding happens because many atoms become more stable when their outer electron shells are filled or closer to full. Sharing is a way to reach that stable arrangement without fully giving electrons away.
Remember
Covalent bonds usually form between nonmetal atoms. The result is a molecule, such as H2O, O2, or CO2.
Key concepts
How many electron pairs are shared?
OO
Double bond
Two electron pairs are shared. Example: oxygen gas, O2.
NN
Triple bond
Three electron pairs are shared. Example: nitrogen gas, N2.
Examples
Three familiar covalent molecules
H
O
H
Water, H2O
Oxygen shares electrons with two hydrogens. The bent shape makes water polar.
O
O
Oxygen, O2
Two oxygen atoms share two pairs of electrons, forming a double bond.
O
C
O
Carbon dioxide, CO2
Carbon shares two pairs with each oxygen. The molecule is linear and nonpolar overall.
Polar vs. nonpolar
In a polar covalent bond, electrons are shared unequally because one atom attracts them more strongly. Water has polar bonds.
In a nonpolar covalent bond, electrons are shared evenly or the molecule's pulls cancel out. O2 is nonpolar because the atoms are identical.
Covalent vs. ionic
| Feature | Covalent | Ionic |
|---|---|---|
| Electron behavior | Shared | Transferred |
| Common atoms | Nonmetal + nonmetal | Metal + nonmetal |
| Typical result | Molecules | Crystal lattices |
Quick check
Test your understanding
Which statement best describes a covalent bond?
Why do atoms share electrons?
Sharing helps atoms reach a more stable outer electron arrangement.
Can one molecule have more than one covalent bond?
Yes. Water has two single covalent bonds, and carbon dioxide has two double covalent bonds.