ionic bond
/ eye-ON-ik bond /
Picture one atom that is greedy for electrons next to another that holds its electrons loosely. The loose one simply hands an electron over to the greedy one. Now one atom is short an electron and carries a positive charge, the other has an extra and carries a negative charge, and opposite charges attract. An ionic bond is the glue that comes from this attraction between oppositely charged atoms, called ions.
When an atom gains or loses electrons it becomes an ion: lose one and you get a positive ion (a cation), gain one and you get a negative ion (an anion). The bond is just plain electric attraction between plus and minus, the same force that makes a rubbed balloon stick to a wall. Because this pull reaches out in every direction equally, ionic bonds are not pointed in any particular direction; instead, vast numbers of positive and negative ions stack into a regular three-dimensional grid where each ion is hugged by neighbors of the opposite sign.
Ionic bonding matters because it explains a whole family of materials — table salt, many minerals, and ceramics — and their shared habits: high melting points, brittleness, and the way they conduct electricity when melted or dissolved but not as dry solids. A common misconception is that an electron is transferred completely and cleanly; in real crystals the sharing is never perfectly all-or-nothing, so most bonds called ionic still keep a little of the character of shared-electron bonds.
In ordinary table salt, each sodium atom gives up one electron to a chlorine atom. The resulting positive sodium ions and negative chlorine ions then arrange themselves into a tidy cube-shaped grid, each ion surrounded by six of the opposite sign — the reason a single salt crystal cleaves into neat little blocks.
In salt, sodium gives an electron to chlorine, and the ions stack into a cubic grid.
An ionic bond is not really a single bond between just two ions. Each ion is pulled on by many neighbors at once, so the true measure of stability is the whole crystal's lattice energy, not one ion pair.