Ionic bonds

When a metal meets a non-metal, electrons are often transferred outright. The metal donates one or more electrons and becomes a positive cation; the non-metal accepts them and becomes a negative anion. Opposite charges attract — and that attraction is the ionic bond.

Table salt is the textbook example. Sodium (Na) hands its single valence electron to chlorine (Cl). Now Na⁺ and Cl⁻ lock together into a rigid crystal lattice — that grid of alternating ions is what a grain of salt actually is.