Chemical bond: definition in chemistry
Chemical bond: A lasting attraction between atoms or ions that holds them together in molecules, crystals and metals.
Bonds form because the bonded arrangement has lower energy than the separate atoms, so making bonds releases energy and breaking them requires it. The three main types are covalent bonds (shared electrons), ionic bonds (attraction between oppositely charged ions) and metallic bonds (metal ions in a sea of electrons). Weaker attractions between molecules, such as hydrogen bonds, are usually treated separately as intermolecular forces.
Examples
- The H–H bond in hydrogen gas — 436 kJ/mol to break
- The N≡N triple bond — about 945 kJ/mol, one of the strongest
- Na⁺ and Cl⁻ ions held together by ionic bonding
- Copper atoms held together by metallic bonding
On the periodic table
The positions of two elements predict how they bond: two nonmetals form covalent bonds, a metal and a nonmetal form ionic bonds, and metals bond to each other through metallic bonding.