chemical bond
/ KEM-ih-kul bond /
Think of a crowd of magnets scattered on a table. Left alone they slide around and clump together wherever they pull on each other. Atoms do something similar: when they come close enough, the electric forces between their electrons and nuclei can lock them into a stable arrangement. A chemical bond is simply that lock — the attraction that holds two or more atoms together so they behave as one piece of matter.
Underneath, every chemical bond is electric. Each atom has a tiny positive nucleus surrounded by negatively charged electrons, and a bond forms when sharing or shifting those electrons lowers the total energy of the group below what it would cost to keep the atoms apart. Nature tends to settle into the lowest-energy arrangement it can reach, so atoms that can lower their energy by sticking together usually do. Chemists name several flavors of bond — sharing electrons, trading them, or pooling them — but all of them are the same underlying electric attraction wearing different clothes.
Chemical bonds matter because they are what turn a loose collection of atoms into water, salt, steel, or you. The strength and direction of these bonds decide whether a material is hard or soft, a conductor or an insulator, brittle or stretchy. A common misconception is that a bond is a physical stick joining two atoms; there is no stick — only a balance of pushes and pulls that happens to favor the atoms staying close, and that balance can be tipped or broken by heat, light, or other chemicals.
Two hydrogen atoms drifting in space hardly notice each other when far apart, but bring them within about a tenth of a nanometer and their electrons rearrange to be shared between both nuclei. The pair drops to a lower energy and snaps into a hydrogen molecule — a single chemical bond holding the two atoms together.
Two hydrogen atoms lower their energy by sharing electrons, forming one bond.
Real bonds rarely fall purely into one category. Most are a blend — partly sharing electrons, partly trading them — so the named types are useful labels rather than sharp, exclusive boxes.